- 问题:在View中对View的context进行强制转换为Activity,报错
2018-02-25 17:38:38 java.lang.ClassCastException: androidx.appcompat.widget.TintContextWrapper cannot be cast to BaseActivity
at com.xx.agent.yy.databinding.ActivityUploadQrCodeBinding._internalCallbackOnClick(ActivityUploadQrCodeBinding.java:313)
at android.databinding.generated.callback.OnClickListener.onClick(OnClickListener.java:11)
at android.view.View.performClick(View.java:4457)
at android.view.View$PerformClick.run(View.java:18496)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5291)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:665)
at dalvik.system.NativeStart.main(Native Method)
- 原因:AppCompat类型的View会对传递进来的Context进行
TintContextWrapper.wrap(context)
包装,如下所示
public class AppCompatImageView extends ImageView implements TintableBackgroundView,
TintableImageSourceView {
....
public AppCompatImageView(
@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(TintContextWrapper.wrap(context), attrs, defStyleAttr);
ThemeUtils.checkAppCompatTheme(this, getContext());
mBackgroundTintHelper = new AppCompatBackgroundHelper(this);
mBackgroundTintHelper.loadFromAttributes(attrs, defStyleAttr);
mImageHelper = new AppCompatImageHelper(this);
mImageHelper.loadFromAttributes(attrs, defStyleAttr);
}
}
TintContextWrapper继承自ContextWrapper,调用wrap包装会将context传递到ContextWrapper的mBase中。所以将View的context强制转换为Activity就会报错。详细可看TintContextWrapper强转Activity失败原因深度探索
要想拿到真正的context,可以使用
private fun getActivity(): Activity? {
var mContext = context
while (mContext is ContextWrapper){
if (mContext is Activity){
return mContext
}
mContext = (context as? ContextWrapper)?.baseContext
}
return null
}