android 常用代码片段

发表于 | 更新于 | 分类于 | 评论数： | 阅读次数：

前言

Android开发过程可能需要用到的代码片段，一共35则。供需要时借鉴参考。

精确获取屏幕尺寸

例如：3.5、4.0、5.0寸屏幕：

1
2
3
4
5
6
public static double getScreenPhysicalSize(Activity ctx) {
        DisplayMetrics dm = new DisplayMetrics();
        ctx.getWindowManager().getDefaultDisplay().getMetrics(dm);
        double diagonalPixels = Math.sqrt(Math.pow(dm.widthPixels, 2) + Math.pow(dm.heightPixels, 2));
        return diagonalPixels / (160 * dm.density);
    }

判断设备是否是平板

一般是7存以上是平板，此为官方用法。

1
2
3
public static boolean isTablet(Context context) {
        return (context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) >= Configuration.SCREENLAYOUT_SIZE_LARGE;
    }

文字根据状态栏更改颜色

属性为:android:textColor
此代码文件放置在项目的res/color/目录下:

1
2
3
4
5
6
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:color="#53c1bd" android:state_selected="true"/>
    <item android:color="#53c1bd" android:state_focused="true"/>
    <item android:color="#53c1bd" android:state_pressed="true"/>
    <item android:color="#777777"/>
</selector>

背景色根据状态更改颜色

属性为:android:backgroup,如果直接给背景色将会报错:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_selected="true"><shape>            
            <gradient android:angle="0" android:centerColor="#00a59f" android:endColor="#00a59f" android:startColor="#00a59f" />
        </shape></item>
    <item android:state_focused="true"><shape>
            <gradient android:angle="0" android:centerColor="#00a59f" android:endColor="#00a59f" android:startColor="#00a59f" />
        </shape></item>
    <item android:state_pressed="true"><shape>
            <gradient android:angle="0" android:centerColor="#00a59f" android:endColor="#00a59f" android:startColor="#00a59f" />
        </shape></item>
    <item><shape>
            <gradient android:angle="0" android:centerColor="#00ff00" android:endColor="00ff00" android:startColor="00ff00" />
        </shape></item>

</selector>

启动App默认的Activity

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
public static void startApkActivity(final Context ctx, String packageName) {
        PackageManager pm = ctx.getPackageManager();
        PackageInfo pi;
        try {
            pi = pm.getPackageInfo(packageName, 0);
            Intent intent = new Intent(Intent.ACTION_MAIN, null);
            intent.addCategory(Intent.CATEGORY_LAUNCHER);
            intent.setPackage(pi.packageName);

            List<ResolveInfo> apps = pm.queryIntentActivities(intent, 0);

            ResolveInfo ri = apps.iterator().next();
            if (ri != null) {
                String className = ri.activityInfo.name;
                intent.setComponent(new ComponentName(packageName, className));
                ctx.startActivity(intent);
            }
        } catch (NameNotFoundException e) {
            Log.e("startActivity", e);
        }
    }

计算字宽

如果设置了textStyle，还需要进一步设置TextPaint。

1
2
3
4
5
public static float GetTextWidth(String text, float Size) {
        TextPaint FontPaint = new TextPaint();
        FontPaint.setTextSize(Size);
        return FontPaint.measureText(text);
    }

获取应用程序下所有的Activity

1
2
3
4
5
6
7
8
9
public static ArrayList<String> getActivities(Context ctx) {
      ArrayList<String> result = new ArrayList<String>();
      Intent intent = new Intent(Intent.ACTION_MAIN, null);
      intent.setPackage(ctx.getPackageName());
      for (ResolveInfo info : ctx.getPackageManager().queryIntentActivities(intent, 0)) {
          result.add(info.activityInfo.name);
      }
      return result;
  }

检测字符串中是否包含汉字

1
2
3
4
5
6
7
8
public static boolean checkChinese(String sequence) {
        final String format = "[\\u4E00-\\u9FA5\\uF900-\\uFA2D]";
        boolean result = false;
        Pattern pattern = Pattern.compile(format);
        Matcher matcher = pattern.matcher(sequence);
        result = matcher.find();
        return result;
    }

检测字符串中只能包含:中文、数字、下划线(_)、横线(-)

1
2
3
4
5
6
public static boolean checkNickname(String sequence) {
        final String format = "[^\\u4E00-\\u9FA5\\uF900-\\uFA2D\\w-_]";
        Pattern pattern = Pattern.compile(format);
        Matcher matcher = pattern.matcher(sequence);
        return !matcher.find();
    }

检查又没有应用程序来接受处理你发出的intent

1
2
3
4
5
6
public static boolean isIntentAvailable(Context context, String action) {
        final PackageManager packageManager = context.getPackageManager();
        final Intent intent = new Intent(action);
        List<ResolveInfo> list = packageManager.queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);
        return list.size() > 0;
    }

使用TransitionDrawable实现渐变效果

比使用AlphaAnimation效果要好，可以避免出现闪烁问题。

1
2
3
4
5
6
7
8
private void setImageBitmap(ImageView imageView, Bitmap bitmap) {
        // Use TransitionDrawable to fade in.
        final TransitionDrawable td = new TransitionDrawable(new Drawable[] { new ColorDrawable(android.R.color.transparent), new BitmapDrawable(mContext.getResources(), bitmap) });
        //noinspection deprecation
            imageView.setBackgroundDrawable(imageView.getDrawable());
        imageView.setImageDrawable(td);
        td.startTransition(200);
    }

扫描指定文件

用途:从本软件新增、修改、删除图片、文件某一个文件（音频、视频）徐奥更新系统媒体库时使用。不必扫描整个SD卡。

1
sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, uri));

Dip转px

用途：难免在Activity代码中设置位置、大小等，本方法就很有用了！ 

1
2
3
public static int dipToPX(final Context ctx, float dip) {
        return (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dip, ctx.getResources().getDisplayMetrics());
    }

获取已经安装的APK路径

代码:

1
2
3
4
5
PackageManager pm = getPackageManager();

        for (ApplicationInfo app : pm.getInstalledApplications(0)) {
             Log.d("PackageList", "package: " + app.packageName + ", sourceDir: " + app.sourceDir);
        }

将会获得以下输出:

1
2
package: com.tmobile.thememanager, sourceDir: /system/app/ThemeManager.apk
        package: com.touchtype.swiftkey, sourceDir: /data/app/com.touchtype.swiftkey-1.apk

多进程Preferences数据共享

1
2
3
4
5
6
7
8
9
10
11
public static void putStringProcess(Context ctx, String key, String value) {
        SharedPreferences sharedPreferences = ctx.getSharedPreferences("preference_mu", Context.MODE_MULTI_PROCESS);
        Editor editor = sharedPreferences.edit();
        editor.putString(key, value);
        editor.commit();
    }

    public static String getStringProcess(Context ctx, String key, String defValue) {
        SharedPreferences sharedPreferences = ctx.getSharedPreferences("preference_mu", Context.MODE_MULTI_PROCESS);
        return sharedPreferences.getString(key, defValue);
    }

泛型ArrayList转数组

1
2
3
4
5
6
7
@SuppressWarnings("unchecked")
    public static <T> T[] toArray(Class<?> cls, ArrayList<T> items) {
        if (items == null || items.size() == 0) {
            return (T[]) Array.newInstance(cls, 0);
        }
        return items.toArray((T[]) Array.newInstance(cls, items.size()));
    }

保存回复ListView当前为位置

可以保存在Preference中或者是数据库中，数据加载完后再设置：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
private void saveCurrentPosition() {
        if (mListView != null) {
            int position = mListView.getFirstVisiblePosition();
            View v = mListView.getChildAt(0);
            int top = (v == null) ? 0 : v.getTop();
            //保存position和top
        }
    }
    
    private void restorePosition() {
        if (mFolder != null && mListView != null) {
            int position = 0;//取出保存的数据
            int top = 0;//取出保存的数据
            mListView.setSelectionFromTop(position, top);
        }
    }

调用便携式热点和数据共享设置

1
2
3
4
5
6
7
public static Intent getHotspotSetting() {
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_MAIN);
        ComponentName com = new ComponentName("com.android.settings", "com.android.settings.TetherSettings");
        intent.setComponent(com);
        return intent;
    }

格式化输出IP地址

1
2
3
public static String getIp(Context ctx) {
        return Formatter.formatIpAddress((WifiManager) ctx.getSystemService(Context.WIFI_SERVICE).getConnectionInfo().getIpAddress());
    }

文件夹排序

先文件夹排序，后文件排序

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
public static void sortFiles(File[] files) {
        Arrays.sort(files, new Comparator<File>() {

            @Override
            public int compare(File lhs, File rhs) {
                //返回负数表示o1 小于o2，返回0 表示o1和o2相等，返回正数表示o1大于o2。 
                boolean l1 = lhs.isDirectory();
                boolean l2 = rhs.isDirectory();
                if (l1 && !l2)
                    return -1;
                else if (!l1 && l2)
                    return 1;
                else {
                    return lhs.getName().compareTo(rhs.getName());
                }
            }
        });
    }

发送不重复的通知（Notification）

关键点在这个requestCode，这里使用的是当前系统时间，巧妙的保证了每次都是一个新的Notification产生。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
public static void sendNotification(Context context, String title,
            String message, Bundle extras) {
        Intent mIntent = new Intent(context, FragmentTabsActivity.class);
        mIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        mIntent.putExtras(extras);

        int requestCode = (int) System.currentTimeMillis();

        PendingIntent mContentIntent = PendingIntent.getActivity(context,
                requestCode, mIntent, 0);

        Notification mNotification = new NotificationCompat.Builder(context)
                .setContentTitle(title).setSmallIcon(R.drawable.app_icon)
                .setContentIntent(mContentIntent).setContentText(message)
                .build();
        mNotification.flags |= Notification.FLAG_AUTO_CANCEL;
        mNotification.defaults = Notification.DEFAULT_ALL;

        NotificationManager mNotificationManager = (NotificationManager) context
                .getSystemService(Context.NOTIFICATION_SERVICE);

        mNotificationManager.notify(requestCode, mNotification);
    }

代码设置TextView的样式

使用过自定义Dialog可能马上会想到用如下代码：

1
new TextView(this,null,R.style.text_style);

但你运行这代码你会发现毫无作用！正确用法：

1
new TextView(new ContextThemeWrapper(this, R.style.text_style));

ip地址转成8位16进制串

ip:192.168.68.128 16 =>hex :c0a84480

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
/** ip转16进制 */
   public static String ipToHex(String ips) {
       StringBuffer result = new StringBuffer();
       if (ips != null) {
           StringTokenizer st = new StringTokenizer(ips, ".");
           while (st.hasMoreTokens()) {
               String token = Integer.toHexString(Integer.parseInt(st.nextToken()));
               if (token.length() == 1)
                   token = "0" + token;
               result.append(token);
           }
       }
       return result.toString();
   }

   /** 16进制转ip */
   public static String texToIp(String ips) {
       try {
           StringBuffer result = new StringBuffer();
           if (ips != null && ips.length() == 8) {
               for (int i = 0; i < 8; i += 2) {
                   if (i != 0)
                       result.append('.');
                   result.append(Integer.parseInt(ips.substring(i, i + 2), 16));
               }
           }
           return result.toString();
       } catch (NumberFormatException ex) {
           Logger.e(ex);
       }
       return "";
   }

WebView保留缩放功能但隐藏缩放控件

注意：setDisplayZoomControls是在API Level 11中新增。

1
2
3
4
mWebView.getSettings().setSupportZoom(true);
       mWebView.getSettings().setBuiltInZoomControls(true);
       if (DeviceUtils.hasHoneycomb())
             mWebView.getSettings().setDisplayZoomControls(false);

获取网络类型名称

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
public static String getNetworkTypeName(Context context) {
       if (context != null) {
           ConnectivityManager connectMgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
           if (connectMgr != null) {
               NetworkInfo info = connectMgr.getActiveNetworkInfo();
               if (info != null) {
                   switch (info.getType()) {
                   case ConnectivityManager.TYPE_WIFI:
                       return "WIFI";
                   case ConnectivityManager.TYPE_MOBILE:
                       return getNetworkTypeName(info.getSubtype());
                   }
               }
           }
       }
       return getNetworkTypeName(TelephonyManager.NETWORK_TYPE_UNKNOWN);
   }

   public static String getNetworkTypeName(int type) {
       switch (type) {
       case TelephonyManager.NETWORK_TYPE_GPRS:
           return "GPRS";
       case TelephonyManager.NETWORK_TYPE_EDGE:
           return "EDGE";
       case TelephonyManager.NETWORK_TYPE_UMTS:
           return "UMTS";
       case TelephonyManager.NETWORK_TYPE_HSDPA:
           return "HSDPA";
       case TelephonyManager.NETWORK_TYPE_HSUPA:
           return "HSUPA";
       case TelephonyManager.NETWORK_TYPE_HSPA:
           return "HSPA";
       case TelephonyManager.NETWORK_TYPE_CDMA:
           return "CDMA";
       case TelephonyManager.NETWORK_TYPE_EVDO_0:
           return "CDMA - EvDo rev. 0";
       case TelephonyManager.NETWORK_TYPE_EVDO_A:
           return "CDMA - EvDo rev. A";
       case TelephonyManager.NETWORK_TYPE_EVDO_B:
           return "CDMA - EvDo rev. B";
       case TelephonyManager.NETWORK_TYPE_1xRTT:
           return "CDMA - 1xRTT";
       case TelephonyManager.NETWORK_TYPE_LTE:
           return "LTE";
       case TelephonyManager.NETWORK_TYPE_EHRPD:
           return "CDMA - eHRPD";
       case TelephonyManager.NETWORK_TYPE_IDEN:
           return "iDEN";
       case TelephonyManager.NETWORK_TYPE_HSPAP:
           return "HSPA+";
       default:
           return "UNKNOWN";
       }
   }

###Android解压Zip包

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
/**
     * 解压一个压缩文档 到指定位置
     * 
     * @param zipFileString 压缩包的名字
     * @param outPathString 指定的路径
     * [url=home.php?mod=space&uid=2643633]@throws[/url] Exception
     */
    public static void UnZipFolder(String zipFileString, String outPathString) throws Exception {
        java.util.zip.ZipInputStream inZip = new java.util.zip.ZipInputStream(new java.io.FileInputStream(zipFileString));
        java.util.zip.ZipEntry zipEntry;
        String szName = "";

        while ((zipEntry = inZip.getNextEntry()) != null) {
            szName = zipEntry.getName();

            if (zipEntry.isDirectory()) {

                // get the folder name of the widget
                szName = szName.substring(0, szName.length() - 1);
                java.io.File folder = new java.io.File(outPathString + java.io.File.separator + szName);
                folder.mkdirs();

            } else {

                java.io.File file = new java.io.File(outPathString + java.io.File.separator + szName);
                file.createNewFile();
                // get the output stream of the file
                java.io.FileOutputStream out = new java.io.FileOutputStream(file);
                int len;
                byte[] buffer = new byte[1024];
                // read (len) bytes into buffer
                while ((len = inZip.read(buffer)) != -1) {
                    // write (len) byte from buffer at the position 0
                    out.write(buffer, 0, len);
                    out.flush();
                }
                out.close();
            }
        }//end of while

        inZip.close();

    }//end of func

从assets中读取文本和图片资源

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
/** 从assets 文件夹中读取文本数据 */
   public static String getTextFromAssets(final Context context, String fileName) {
       String result = "";
       try {
           InputStream in = context.getResources().getAssets().open(fileName);
           // 获取文件的字节数
           int lenght = in.available();
           // 创建byte数组
           byte[] buffer = new byte[lenght];
           // 将文件中的数据读到byte数组中
           in.read(buffer);
           result = EncodingUtils.getString(buffer, "UTF-8");
           in.close();
       } catch (Exception e) {
           e.printStackTrace();
       }
       return result;
   }
   
   /** 从assets 文件夹中读取图片 */
   public static Drawable loadImageFromAsserts(final Context ctx, String fileName) {
       try {
           InputStream is = ctx.getResources().getAssets().open(fileName);
           return Drawable.createFromStream(is, null);
       } catch (IOException e) {
           if (e != null) {
               e.printStackTrace();
           }
       } catch (OutOfMemoryError e) {
           if (e != null) {
               e.printStackTrace();
           }
       } catch (Exception e) {
           if (e != null) {
               e.printStackTrace();
           }
       }
       return null;
   }

展开、收起状态栏

用途：可用于点击Notifacation之后收起状态栏

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
public static final void collapseStatusBar(Context ctx) {
        Object sbservice = ctx.getSystemService("statusbar");
        try {
            Class<?> statusBarManager = Class.forName("android.app.StatusBarManager");
            Method collapse;
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
                collapse = statusBarManager.getMethod("collapsePanels");
            } else {
                collapse = statusBarManager.getMethod("collapse");
            }
            collapse.invoke(sbservice);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static final void expandStatusBar(Context ctx) {
        Object sbservice = ctx.getSystemService("statusbar");
        try {
            Class<?> statusBarManager = Class.forName("android.app.StatusBarManager");
            Method expand;
            if (Build.VERSION.SDK_INT >= 17) {
                expand = statusBarManager.getMethod("expandNotificationsPanel");
            } else {
                expand = statusBarManager.getMethod("expand");
            }
            expand.invoke(sbservice);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

获取状态栏高度

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
public static int getStatusBarHeight(Context context){
        Class<?> c = null;
        Object obj = null;
        Field field = null;
        int x = 0, statusBarHeight = 0;
        try {
            c = Class.forName("com.android.internal.R$dimen");
            obj = c.newInstance();
            field = c.getField("status_bar_height");
            x = Integer.parseInt(field.get(obj).toString());
            statusBarHeight = context.getResources().getDimensionPixelSize(x);
        } catch (Exception e1) {
            e1.printStackTrace();
        }
        return statusBarHeight;
    }

ListView使用ViewHolder极简写法

用起来非常简练，将ViewHolder隐于无形。

1
2
3
4
5
6
7
8
9
10
11
12
13
public static <T extends View> T getAdapterView(View convertView, int id) {
        SparseArray<View> viewHolder = (SparseArray<View>) convertView.getTag();
        if (viewHolder == null) {
            viewHolder = new SparseArray<View>();
            convertView.setTag(viewHolder);
        }
        View childView = viewHolder.get(id);
        if (childView == null) {
            childView = convertView.findViewById(id);
            viewHolder.put(id, childView);
        }
        return (T) childView;
    }

用法:

1
2
3
4
5
6
7
8
9
@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(getActivity()).inflate(R.layout.fragment_feed_item, parent, false);
        }

        ImageView thumnailView = getAdapterView(convertView, R.id.video_thumbnail);
        ImageView avatarView =  getAdapterView(convertView, R.id.user_avatar);
        ImageView appIconView = getAdapterView(convertView, R.id.app_icon);

设置Activity透明

说明：AppBaseTheme一般是你application指定的android:theme是啥这里就是啥，否则Activity内部的空间风格可能不一致。
用途：用于模拟Dialog效果，比如再Service中没法用Dialog，就可以用Activity来模拟。

1
2
3
4
5
6
7
<style name="TransparentActivity" parent="AppBaseTheme">
    <item name="android:windowBackground">@android:color/transparent</item>
    <item name="android:colorBackgroundCacheHint">@null</item>
    <item name="android:windowIsTranslucent">true</item>
    <item name="android:windowNoTitle">true</item>
    <item name="android:windowContentOverlay">@null</item>
</style>

代码切换全屏

注意：切换到全屏时，底部的虚拟按键仍然是显示的。次方法可多次调用用于切换.
用途：播放器界面经常会用到.

1
2
3
4
5
6
7
//切换到全屏
        getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN);
        getActivity().getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);

        //切换到非全屏
        getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN);

调用开发者选项中显示触摸位置功能

设置1显示，设置0不显示。

1
android.provider.Settings.System.putInt(getContentResolver(), "show_touches", 1);

获取设备上已安装并且可启动的应用列表

注意：使用getInstalledApplications会返回很多无法启动甚至没有图标的系统应用。ResolveInfo.activityInfo.applicationInfo也能取到你想要的数据。

1
2
3
4
Intent intent = new Intent(Intent.ACTION_MAIN);
            intent.addCategory(Intent.CATEGORY_LAUNCHER);

            List<ResolveInfo> activities = getPackageManager().queryIntentActivities(intent, 0)
本文摘抄自eoe论坛,非本博原创。
0%