Programming►Android
Programming

App crash issue when inflating ViewPager

I wrote a very simple layout file with a ViewPager, but the app crashes when inflating it.

Layout file
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<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ViewPager
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</FrameLayout>

Here is the error message:

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04-22 22:27:00.828    1128-1479/com.github.timnew.rubiktimer E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.github.timnew.rubiktimer, PID: 1128
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.github.timnew.rubiktimer/com.github.timnew.rubiktimer.history.HistoryActivity_}: android.view.InflateException: Binary XML file line #7: Error inflating class ViewPager
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2282)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2340)
            at android.app.ActivityThread.access$800(ActivityThread.java:157)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:157)
            at android.app.ActivityThread.main(ActivityThread.java:5293)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: android.view.InflateException: Binary XML file line #7: Error inflating class ViewPager
            at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:713)
            at android.view.LayoutInflater.rInflate(LayoutInflater.java:761)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:498)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:398)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:354)
            at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:340)
            at com.actionbarsherlock.internal.ActionBarSherlockNative.setContentView(ActionBarSherlockNative.java:134)
            at com.actionbarsherlock.app.SherlockFragmentActivity.setContentView(SherlockFragmentActivity.java:262)
            at com.github.timnew.rubiktimer.history.HistoryActivity_.setContentView(HistoryActivity_.java from OutputFileObject:44)
            at com.github.timnew.rubiktimer.history.HistoryActivity_.onCreate(HistoryActivity_.java from OutputFileObject:34)
            at android.app.Activity.performCreate(Activity.java:5389)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2246)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2340)
            at android.app.ActivityThread.access$800(ActivityThread.java:157)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:157)
            at android.app.ActivityThread.main(ActivityThread.java:5293)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.ViewPager" on path: DexPathList[[zip file "/data/app/com.github.timnew.rubiktimer-76.apk"],nativeLibraryDirectories=[/data/app-lib/com.github.timnew.rubiktimer-76, /vendor/lib, /system/lib]]
            at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:67)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:497)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:457)
            at android.view.LayoutInflater.createView(LayoutInflater.java:565)
            at android.view.LayoutInflater.onCreateView(LayoutInflater.java:658)
            at com.android.internal.policy.impl.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:66)
            at android.view.LayoutInflater.onCreateView(LayoutInflater.java:675)
            at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:700)
            at android.view.LayoutInflater.rInflate(LayoutInflater.java:761)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:498)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:398)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:354)
            at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:340)
            at com.actionbarsherlock.internal.ActionBarSherlockNative.setContentView(ActionBarSherlockNative.java:134)
            at com.actionbarsherlock.app.SherlockFragmentActivity.setContentView(SherlockFragmentActivity.java:262)
            at com.github.timnew.rubiktimer.history.HistoryActivity_.setContentView(HistoryActivity_.java from OutputFileObject:44)
            at com.github.timnew.rubiktimer.history.HistoryActivity_.onCreate(HistoryActivity_.java from OutputFileObject:34)
            at android.app.Activity.performCreate(Activity.java:5389)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2246)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2340)
            at android.app.ActivityThread.access$800(ActivityThread.java:157)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:157)
            at android.app.ActivityThread.main(ActivityThread.java:5293)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
            at dalvik.system.NativeStart.main(Native Method)

According to the message, we can figure out that the issue is caused because Android cannot found the class android.view.ViewPager.

If we’re careful enough, we can figure out that there is something wrong with the ViewPager fullname. Since ViewPager isn’t a standard widget, so it is provided in Support Library instead in the core SDK. So it is not in the package of android.view, it is in the pacakge android.support.v4.view.

To fix the issue, we should not reference the ViewPager with plain name but with the full name android.support.v4.view.ViewPager.

So this is the updated layout xml:

Fixed Lyaout
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<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.v4.view.ViewPager
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</FrameLayout>
Programming►Android
Programming

Android SQLite database requires special table

I’m working on an Android application recently. During the development, our new app inherited a legacy SQLite database that created by a WinCE application.

Android announce that it supports the SQLite database, so we don’t worry about that too much. But when we try to open the legacy database with SQLiteDatabase.openDatabase, it throws exception on our face!

After debugging, we found to open SQLite database with SQLiteDatabase class requires the database to have a special table called android_metadata, which contains the locale information. And SQLiteDatabase yields exception when the table cannot be found.

The table will be created automatically when SQLiteDatabase creates the database, but if the app need to open the database not created by android, some patch is needed.

Here is the script to patch the database:

Patch Database
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CREATE TABLE android_metadata (locale TEXT);
INSERT INTO android_metadata VALUES('en-US');