Some Useful Android Programming Snips

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;
}

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;
}

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();
}

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;
}

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);
}

/**
  * 将px值转换为dip或dp值，保证尺寸大小不变
  * 
  * @param pxValue
  * @param scale（DisplayMetrics类中属性density）
  * @return
  */
public static int px2dip(float pxValue, float scale) {
    return (int) (pxValue / scale + 0.5f);
}

/**
* 将dip或dp值转换为px值，保证尺寸大小不变
* 
* @param dipValue
* @param scale（DisplayMetrics类中属性density）
* @return
*/
public static int dip2px(float dipValue, float scale) {
  return (int) (dipValue * scale + 0.5f);
}

/**
* 将px值转换为sp值，保证文字大小不变
* 
* @param pxValue
* @param fontScale（DisplayMetrics类中属性scaledDensity）
* @return
*/
public static int px2sp(float pxValue, float fontScale) {
    return (int) (pxValue / fontScale + 0.5f);
}

/**
* 将sp值转换为px值，保证文字大小不变
* 
* @param spValue
* @param fontScale（DisplayMetrics类中属性scaledDensity）
* @return
*/
public static int sp2px(float spValue, float fontScale) {
    return (int) (spValue * fontScale + 0.5f);
}

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);
}

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

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);
    }
}

public static float GetTextWidth(String text, float Size) {
    TextPaint FontPaint = new TextPaint();
    FontPaint.setTextSize(Size);
    return FontPaint.measureText(text);
}
（注意如果设置了textStyle，还需要进一步设置TextPaint。）

/**
 * 半角转全角
 * 
 * @param input
 *            String.
 * @return 全角字符串.
 */
public static String ToSBC(String input) {
    char c[] = input.toCharArray();
    for (int i = 0; i < c.length; i++) {
        if (c[i] == ' ') {
            c[i] = 'u3000'; // 采用十六进制,相当于十进制的12288

        } else if (c[i] < '177') { // 采用八进制,相当于十进制的127
            c[i] = (char) (c[i] + 65248);

        }
    }
    return new String(c);
}

/**
 * 全角转半角
 * 
 * @param input
 *            String.
 * @return 半角字符串
 */
public static String ToDBC(String input) {

    char c[] = input.toCharArray();
    for (int i = 0; i < c.length; i++) {
        if (c[i] == 'u3000') {
            c[i] = ' ';
        } else if (c[i] > 'uFF00' && c[i] < 'uFF5F') {
            c[i] = (char) (c[i] - 65248);

        }
    }
    String returnString = new String(c);

    return returnString;
}

int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);  
Log.d("TAG", "Max memory is " + maxMemory + "KB");

/**
 * 将一个输入流转换成制定编码的字符串
 * 
 * @param @param inputStream
 * @param @param encode
 */
private static String changeInputStream(InputStream inputStream,
        String encode) {
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    byte[] data = new byte[1024];
    int len = 0;
    String result = "";
    if (inputStream != null) {
        try {
            while ((len = inputStream.read(data)) != -1) {
                outputStream.write(data, 0, len);
            }
            result = new String(outputStream.toByteArray(), encode);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return result;
}

TextView textView = (TextView)findViewById(R.id.textview);  
  
// Method 1:  
textView.setText(Html.fromHtml("<font color=\"#ff0000\">红色</font>其它颜色"));  
  
// Method 2: 
String text = "获得银宝箱!";  
SpannableStringBuilder style=new SpannableStringBuilder(text);     
style.setSpan(new BackgroundColorSpan(Color.RED),2,5,Spannable.SPAN_EXCLUSIVE_INCLUSIVE);     //设置指定位置textview的背景颜色  
style.setSpan(new ForegroundColorSpan(Color.RED),0,2,Spannable.SPAN_EXCLUSIVE_INCLUSIVE);     //设置指定位置文字的颜色  
textView.setText(style);

String text = String.format(getResources().getString(R.string.baoxiang), 2,18,"银宝箱");

<string name="baoxiang">您今天打了%1$d局,还差%2$d局可获得%3$s!</string>  
%1$d表达的意思是整个name=”<span style="white-space: pre;">baoxiang</span>”字符串中，第一个整型%1$d表达的意思是整个name=”<span style="white-space: pre;">baoxiang</span>”字符串中，第一个整型

@Override
public boolean onTouch(View v, MotionEvent event) {
    if (event.getAction()==MotionEvent.ACTION_DOWN) {
        categoryImageView.setAlpha(0.5f);
    }
    if (event.getAction()==MotionEvent.ACTION_UP || 
            event.getAction()==MotionEvent.ACTION_CANCEL) {
        categoryImageView.setAlpha(1.0f);
    }
    return true;
}