Create a md5 hash from a string

Reference:

https://dzone.com/articles/android-snippet-making-md5

Code snippet:

public static String encryptByMd5Hash(String in) {
    String md5 = "";
    MessageDigest digest;
    try {
        digest = MessageDigest.getInstance("MD5");
        digest.reset();
        digest.update(in.getBytes());
        byte[] a = digest.digest();
        int len = a.length;
        StringBuilder sb = new StringBuilder(len << 1);
        for (int i = 0; i < len; i++) {
            sb.append(Character.forDigit((a[i] & 0xf0) >> 4, 16));
            sb.append(Character.forDigit(a[i] & 0x0f, 16));
        }
        md5 = sb.toString();
    } catch (NoSuchAlgorithmException e){
        e.printStackTrace();
    }
    return md5;
}

Fix "SecurityException: Binder invocation to an incorrect interface using in-app billing" when bind remote AIDL service

Reference:

http://blog.csdn.net/a1031359915/article/details/7785227

Description:

當 client app使用AIDL向 server app請求服務的時後，client app和 server app的 AIDL package name要一模一樣，否則在執行的時後，就會跳出 SecurityException: Binder invocation to an incorrect interface using in-app billing的錯誤訊息

Set window flag by reflection

Reference:

http://stackoverflow.com/questions/10555407/android-how-to-get-an-instance-of-a-member-field-via-reflection
http://stackoverflow.com/questions/32218419/how-i-can-access-inner-class-variable-value-using-reflection-in-java
http://www.qingpingshan.com/m/view.php?aid=125698

Description:

為了讓 system dialog可以在 multi user裡顯示，必須要設定 PRIVATE_FLAG_SHOW_FOR_ALL_USERS flag，但是因為 setPrivateFlags是 Window.java的 hide API，PRIVATE_FLAG_SHOW_FOR_ALL_USERS是 WindowManager的 hide variable，除了直接 import framework.jar之外，還可以透過 reflection的機制

Code Snippet:

public static final int FRAMEWORK_PRIVATE_FLAG_SHOW_FOR_ALL_USERS = 0x00000010;
public static void setShowForAllUsers(Window window) {
    LogTool.d(TAG, "setShowForAllUsers");
    Class<?> windowClass = null;
    Class<?> windowManagerClass = null;
    try {
        try {
            windowClass = Class.forName("android.view.Window");
            windowManagerClass = Class.forName("android.view.WindowManager");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        try {
            Method method = windowClass.getDeclaredMethod("setPrivateFlags", int.class, int.class);
            method.setAccessible(true);

            try {
                try {
                    int allUsersFlag = FRAMEWORK_PRIVATE_FLAG_SHOW_FOR_ALL_USERS;
                    Class<?>[] classes = windowManagerClass.getDeclaredClasses();
                    for(Class innerClass: classes){
                        if(innerClass.getName().contains("LayoutParams")){
                            Field field = innerClass.getDeclaredField("PRIVATE_FLAG_SHOW_FOR_ALL_USERS");
                            field.setAccessible(true);
                            allUsersFlag = field.getInt(window.getAttributes());
                            break;
                        }
                    }
                    LogTool.d(TAG, "allUsersFlag: " + allUsersFlag + " ; hex: " + Integer.toHexString(allUsersFlag));

                    method.invoke(window, allUsersFlag, allUsersFlag);
                } catch (InvocationTargetException e) {
                    e.printStackTrace();
                }
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        } catch (NullPointerException e1) {
            e1.printStackTrace();
        }
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch(NoSuchFieldException nsfe){
        nsfe.printStackTrace();
    }
}

Android 6.0+ 請求 SYSTEM_ALERT_WINDOW權限

Reference:

http://stackoverflow.com/questions/32652533/android-system-overlay-window
http://caiyao.name/2016/03/02/Android-6-0%E8%BF%90%E8%A1%8C%E6%97%B6%E6%9D%83%E9%99%90%E5%B0%8F%E7%BB%93/

Error message:

Unable to add window android.view.ViewRoot$W@XXXXXXXX — permission denied for this window type

Code snippet:

在 Android 6.0+ (SDK 23+) 用 TYPE_SYSTEM_ALERT，即使在 Manifest裡有宣告 permission

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

依舊會出現上面的 Error message.
這時候要先透過 Settings.canDrawOverlays檢查 app是否有權限，如果沒有的話，發出 Settings.ACTION_MANAGE_OVERLAY_PERMISSION 的 Intent，讓使用者打開權限

@Overrideprotected void onResume() {
    super.onResume();

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if(!Settings.canDrawOverlays(this)){
            requestAlertWindowPermission();
        } else{
            // do something
        }
    } else{
        // do something
    }
}

private static final int REQUEST_CODE = 1;
private  void requestAlertWindowPermission() {
    Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
    intent.setData(Uri.parse("package:" + getPackageName()));
    startActivityForResult(intent, REQUEST_CODE);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == REQUEST_CODE) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (Settings.canDrawOverlays(this)) {
                Log.i(TAG, "onActivityResult granted");
                // do something
            } else{
                Log.i(TAG, "onActivityResult not granted");
            }
        }
    }
}

Turning on screen and keep screen lon

Reference:

http://stackoverflow.com/questions/2891337/turning-on-screen-programmatically

Advance:
Turn on screen and dismiss keyguard
http://stackoverflow.com/questions/30246425/turning-on-screen-from-receiver-service

Code snippet:

在需要打開螢幕的地方加入下面的 code
WakeLock wl = ((PowerManager)getSystemService(POWER_SERVICE)).newWakeLock(
     PowerManager.SCREEN_BRIGHT_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP, "TAG");
wl.acquire();

在離開前要記得釋放 wake lock，以免螢幕保持開啟，造成耗電的問題
wl.release();

Note:
釋放 (release)的 wake lock要和獲取 (acquire)的是同一個，不要再重新建立一個新的wake lock，否則釋放 wake lock時會不能正常運作

解決 Android minSDK支援的問題

Reference: 

http://droidyue.com/blog/2015/07/25/use-android-lint-to-find-higher-api-usage/

 

 

說明：

要解決minSDK支援的問題,可以使用Lint來找出哪些高版本API並不支援在低版本.

 

在Android Sutdio中

選擇功能表Analyze—>Configure Current File Analysis—>Configure Inspections 清空所有的檢查項，然後如下圖勾選Calling new methods on older versions 和 Using inlined constants on older versions

 

 

在這個專案中, 我們希望mini SDK能支援到 19.

 

 

執行Lint找出有問題的API,

Analyze>Inspect Code…>Whole project>OK

 

 

 在該專案中找到41個items, 現在你可以方便地去修正問題了.

 

Detect if TextVIew is ellipsized

Code snippet
//Hide/Show More buttion
final TextView detail   = (TextView) findViewById(R.id.detail);
final TextView more     = (TextView) findViewById(R.id.more);
ViewTreeObserver vto = detail.getViewTreeObserver();
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
        @Override
        public boolean onPreDraw() {
                ViewTreeObserver observer = detail.getViewTreeObserver();
                observer.removeOnPreDrawListener(this);
                String text         = detail.getText().toString();
                String layoutText   = detail.getLayout().getText().toString();
                more.setVisibility((!text.equals(layoutText)) ? View.VISIBLE:View.INVISIBLE);
                return true;
        }
});