Android 实用代码片段，

Android 实用代码片段，

一些不常见确又很实用的代码块。

1.精确获取屏幕尺寸（例如：3.5、4.0、5.0寸屏幕）

 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);
    }

2.判断是否是平板（官方用法）

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

3.文字根据状态更改颜色 android:textColor

<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>

4.背景色根据状态更改颜色 android:backgroup(如果直接给背景色color会报错)

<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>

5.启动APK的默认Activity

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);
        }
    }

6.计算字宽(注意如果设置了textStyle，还需要进一步设置TextPaint)

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

7.获取应用程序下所有Activity

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;
  }

8.检测字符串中是否包含汉字

 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;
    }

9.检测字符串中只能包含：中文、数字、下划线(_)、横线(-)

 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();
    } 

10.检查有没有应用程序来接受处理你发出的intent

  public static boolean isIntentAvailable(Context context, String action) {
        final PackageManager packageManager = cont