Seven sections of Android utility code

Keywords: Android

Welcome to reprint, but please keep the original source of the article:)
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Uncle farmer:

1. Accurately obtain screen size (for example: 3.5, 4.0, 5.0 inch screen)

public static double getScreenPhysicalSize(Activity ctx) {

        DisplayMetrics dm = new DisplayMetrics();


        double diagonalPixels = Math.sqrt(Math.pow(dm.widthPixels, 2) + Math.pow(dm.heightPixels, 2));

        return diagonalPixels / (160 * dm.density);


Generally, it's a flat plate over 7 inches

2. Judge whether it is a tablet (official use)

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

3. Change the color of text according to the status android:textColor

Under res/color /

<selector xmlns: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"/>


4. The background color changes according to the status android:backgroup

If you give the background color directly, an error will be reported.

<selector xmlns:android="">

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



5. Start APK's default 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);

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

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

6. Calculate word width

Note that if textStyle is set, further TextPaint needs to be set.  

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


Posted by jlpulido on Sun, 03 Nov 2019 09:24:22 -0800