android - ActivityThread.handleBindApplication 中的 NullPointerException

Question

我收到了这份堆栈跟踪报告，其中根本没有提及我的应用:

java.lang.NullPointerException
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:3979)
at android.app.ActivityThread.access$1300(ActivityThread.java:130)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1255)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)

有人知道如何防止这种异常吗？

Answer 1

一如既往，当发生这种情况时，我必须深入研究 Android 源代码来评估问题，我想我会在这里发布我的发现，这样可以节省其他人的时间。

此错误对应于 4.1.1_r1 中的此代码和 4.1.2_r1 :

    final ContextImpl appContext = new ContextImpl();
    appContext.init(data.info, null, this);
    final File cacheDir = appContext.getCacheDir();

    // Provide a usable directory for temporary files
    System.setProperty("java.io.tmpdir", cacheDir.getAbsolutePath()); // line 3979

    setupGraphicsSupport(data.info, cacheDir);

发生这种情况是因为 appContext.getCacheDir()在某些情况下返回 null:

@Override
public File getCacheDir() {
    synchronized (mSync) {
        if (mCacheDir == null) {
            mCacheDir = new File(getDataDirFile(), "cache");
        }
        if (!mCacheDir.exists()) {
            if(!mCacheDir.mkdirs()) {
                Log.w(TAG, "Unable to create cache directory");
                return null;
            }
            FileUtils.setPermissions(
                    mCacheDir.getPath(),
                    FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IXOTH,
                    -1, -1);
        }
    }
    return mCacheDir;
}

相关: https://groups.google.com/forum/?fromgroups=#!topic/android-developers/-694j87eXVU

---

然而，这似乎在 4.2.1 版本中得到了正确处理:

    final ContextImpl appContext = new ContextImpl();
    appContext.init(data.info, null, this);
    if (!Process.isIsolated()) {
        final File cacheDir = appContext.getCacheDir();

        if (cacheDir != null) {
            // Provide a usable directory for temporary files
            System.setProperty("java.io.tmpdir", cacheDir.getAbsolutePath());

            setupGraphicsSupport(data.info, cacheDir);
        } else {
            Log.e(TAG, "Unable to setupGraphicsSupport due to missing cache directory");
        }
    }