Android 7.1.1 Toast引起的Crash
背景
最近一直做国际化项目，用户使用的手机都是android中低档手机，出现的问题也比较奇葩，最近项目刚上线就遇到了一个crash
android.view.WindowManager$BadTokenException: Unable to add window -- token android.os.BinderProxy@bf0c2d7 is not valid; is your activity running?
at android.view.ViewRootImpl.setView(ViewRootImpl.java:797)
at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:351)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:93)
at android.widget.Toast$TN.handleShow(Toast.java:465)
at android.widget.Toast$TN$2.handleMessage(Toast.java:347)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:203)
at android.app.ActivityThread.main(ActivityThread.java:6337)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1084)
初步分析
最开始我以为是dialog或者popwindow引起的问题，我还找相关同事排查了一下，发现不是，通过log堆栈分析是Toast引起的问题，这个奇怪了，这个项目的代码之前一直在国内运行，一直没有发现过这个问题，如果是项目中Toast使用问题应该早就发现了？？
搜索相关资料
在网上找了写相关资料，也有不少网友遇到类似的问题，问题都是集中在Android7.1.1和Android7.1.2机型上，出问题的机型正好是Android7.1.1手机！先看看到底是什么原因引起的吧
Android7.1.1出现问题的原因
先来看看前辈的解答吧
答案.png
总结一下，这个问题可以算是android 系统为了优化系统，才引起了bug，好在8.0的系统上已经发现这个问题已经try-catch修复了，最起码不导致崩溃了
截取了一段Toast的源代码（Android8.0 的源码），已经处理了
public void handleShow(IBinder windowToken) {
if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView
+ " mNextView=" + mNextView);
// If a cancel/hide is pending - no need to show - at this point
// the window token is already invalid and no need to do any work.
if (mHandler.hasMessages(CANCEL) || mHandler.hasMessages(HIDE)) {
return;
}
if (mView != mNextView) {
// remove the old view if necessary
handleHide();
mView = mNextView;
Context context = mView.getContext().getApplicationContext();
String packageName = mView.getContext().getOpPackageName();
if (context == null) {
context = mView.getContext();
}
mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
// We can resolve the Gravity here by using the Locale for getting
// the layout direction
final Configuration config = mView.getContext().getResources().getConfiguration();
final int gravity = Gravity.getAbsoluteGravity(mGravity, config.getLayoutDirection());
mParams.gravity = gravity;
if ((gravity & Gravity.HORIZONTAL_GRAVITY_MASK) == Gravity.FILL_HORIZONTAL) {
mParams.horizontalWeight = 1.0f;
}
if ((gravity & Gravity.VERTICAL_GRAVITY_MASK) == Gravity.FILL_VERTICAL) {
mParams.verticalWeight = 1.0f;
}
mParams.x = mX;
mParams.y = mY;
mParams.verticalMargin = mVerticalMargin;
mParams.horizontalMargin = mHorizontalMargin;
mParams.packageName = packageName;
mParams.hideTimeoutMilliseconds = mDuration ==
Toast.LENGTH_LONG ? LONG_DURATION_TIMEOUT : SHORT_DURATION_TIMEOUT;
mParams.token = windowToken;
if (mView.getParent() != null) {
if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this);
mWM.removeView(mView);
}
if (localLOGV) Log.v(TAG, "ADD! " + mView + " in " + this);
// Since the notification manager service cancels the token right
// after it notifies us to cancel the toast there is an inherent
// race and we may attempt to add a window after the token has been
// invalidated. Let us hedge against that.
try {
mWM.addView(mView, mParams);
trySendAccessibilityEvent();
} catch (WindowManager.BadTokenException e) {
/* ignore */
//关键的地方，已经catch住了
}
}
}
如果要从根本上解决这类问题还是比较难的，因为要排查系统中哪些地方导致 了主线程阻塞住了，但是如果直接解决这个崩溃问题还是比较简单的
解决方案
网上有一个解决这个问题的[开源库]https://github.com/drakeet/ToastCompat)
思路：
So I created this library, and replace the base Context to a SafeToastContext, it will hook the WindowManagerWrapper.addView(view, params) method and fix the exception.
实际上就是Hook住了系统WindowManager的addview方法，对这个方式try-catch处理了
文件分析：主要就三个文件
文件目录.png
使用方式
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.Toast;
import me.drakeet.support.toast.ToastCompat;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ToastCompat.makeText(this, "hello", Toast.LENGTH_SHORT)
.setBadTokenListener(toast -> {
Log.e("failed toast", "hello");
}).show();
}
}
对弹出Toast地方，都使用统一的ToastCompat方式，我们看一下ToastCompat是什么吧？
ToastCompat就是对Toast的代理也可以称之为委托，先看一下关键方法makeText
public static ToastCompat makeText(Context context, CharSequence text, int duration) {
// We cannot pass the SafeToastContext to Toast.makeText() because
// the View will unwrap the base context and we are in vain.
@SuppressLint("ShowToast")
Toast toast = Toast.makeText(context, text, duration);
setContextCompat(toast.getView(), new SafeToastContext(context, toast));
return new ToastCompat(context, toast);
}
首先创建了一个Toast对象，然后又调用了setContextCompat方法
private static void setContextCompat(@NonNull View view, @NonNull Context context) {
if (Build.VERSION.SDK_INT == 25) {
try {
Field field = View.class.getDeclaredField("mContext");
field.setAccessible(true);
field.set(view, context);
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
}
把ToastView context 给替换了
final class SafeToastContext extends ContextWrapper {
private @NonNull Toast toast;
private @Nullable BadTokenListener badTokenListener;
SafeToastContext(@NonNull Context base, @NonNull Toast toast) {
super(base);
this.toast = toast;
}
@Override
public Context getApplicationContext() {
return new ApplicationContextWrapper(getBaseContext().getApplicationContext());
}
public void setBadTokenListener(@NonNull BadTokenListener badTokenListener) {
this.badTokenListener = badTokenListener;
}
关键的是getApplicationContext 这个方法
private final class ApplicationContextWrapper extends ContextWrapper {
private ApplicationContextWrapper(@NonNull Context base) {
super(base);
}
@Override
public Object getSystemService(@NonNull String name) {
if (Context.WINDOW_SERVICE.equals(name)) {
// noinspection ConstantConditions
return new WindowManagerWrapper((WindowManager) getBaseContext().getSystemService(name));
}
return super.getSystemService(name);
}
}
实际上在获取系统中WindowManager的时候，是获取了我们包装类的
WindowManagerWrapper，在这个类中我们对addView 增加了try-catch的操作
private final class WindowManagerWrapper implements WindowManager {
private static final String TAG = "WindowManagerWrapper";
private final @NonNull WindowManager base;
private WindowManagerWrapper(@NonNull WindowManager base) {
this.base = base;
}
@Override
public Display getDefaultDisplay() {
return base.getDefaultDisplay();
}
@Override
public void removeViewImmediate(View view) {
base.removeViewImmediate(view);
}
@Override
public void addView(View view, ViewGroup.LayoutParams params) {
try {
Log.d(TAG, "WindowManager's addView(view, params) has been hooked.");
base.addView(view, params);
} catch (BadTokenException e) {
Log.i(TAG, e.getMessage());
if (badTokenListener != null) {
badTokenListener.onBadTokenCaught(toast);
}
} catch (Throwable throwable) {
Log.e(TAG, "[addView]", throwable);
}
}
@Override
public void updateViewLayout(View view, ViewGroup.LayoutParams params) {
base.updateViewLayout(view, params);
}
@Override
public void removeView(View view) {
base.removeView(view);
}
}
总结：代码并不复杂，逻辑比较清晰，实现的思路也是比较有趣的
疑问：
- Toast的实现原理是什么呢？
- ContextWrapper 是什么呢？
- ContextWrapper 中getApplicationContext 返回的是什么呢
为什么会有这些疑问，一般对疑难的crash问题我都喜欢刨根问底，探究问题根源对问题的执着会让你在过程中收获很多问题，以上问题就是我在专研这类问题的时候遇到的相关知识,有写知识之前都看过但是随着时间的流逝也都不记得了
引用
大家有没有遇到过只在 Android 7.1 机型上报告的由Toast引起的BadTokenException错误？
github 上解决方案
Toast与Snackbar的那点事
Android7.1.1Toast崩溃解决方案