java - onActivityResult 拍照时返回空指针异常？

Question

我正在尝试将其与我的应用程序集成:Capture Image from Camera and Display in Activity

当我打开 Activity 时，我完全使用了作者所写的内容，但出现了空指针异常。 logcat 如下所示:

11-20 15:03:13.178: D/AndroidRuntime(15052): Shutting down VM
11-20 15:03:13.178: W/dalvikvm(15052): threadid=1: thread exiting with uncaught exception (group=0x400259f8)
11-20 15:03:13.189: E/AndroidRuntime(15052): FATAL EXCEPTION: main
11-20 15:03:13.189: E/AndroidRuntime(15052): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dummies.android.taskreminder/com.dummies.android.taskreminder.activity.UsersThoughts}: java.lang.ClassCastException: android.widget.Button
11-20 15:03:13.189: E/AndroidRuntime(15052):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2787)
11-20 15:03:13.189: E/AndroidRuntime(15052):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2803)

所以我尝试对其进行一些更改，现在每当我从拍照返回到我的 Activity 时，当我使用此配置时，我都会收到空指针异常:

//in oncreate       
this.imageView = new ImageView(this);
this.imageView = (ImageView) this.imageView.findViewById(R.id.camera_thought);


//method in class file
protected void onActivityResult(int requestCode, int resultCode, Intent data) {  
    if (requestCode == CAMERA_REQUEST && resultCode == RESULT_OK) {  
        Bitmap photo = (Bitmap) data.getExtras().get("data"); 
        imageView.setImageBitmap(photo);
    }  
}

错误如下所示:

11-20 14:53:39.118: D/AndroidRuntime(14931): Shutting down VM
11-20 14:53:39.118: W/dalvikvm(14931): threadid=1: thread exiting with uncaught exception (group=0x400259f8)
11-20 14:53:39.128: E/AndroidRuntime(14931): FATAL EXCEPTION: main
11-20 14:53:39.128: E/AndroidRuntime(14931): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1888, result=-1, data=Intent { act=inline-data dat=content://media/external/images/media/89 (has extras) }} to activity {com.dummies.android.taskreminder/com.dummies.android.taskreminder.activity.UsersThoughts}: java.lang.NullPointerException
11-20 14:53:39.128: E/AndroidRuntime(14931):    at android.app.ActivityThread.deliverResults(ActivityThread.java:3734)

Answer 1

问题是 imageView 在您的 onCreate() 方法之后将为 null。

看起来您在分配它时混合了一些不同的约定。通常，在扩充布局文件时会调用 findViewById()。您可能有某种布局，某种 R.layout.my_layout 形式，因此请尝试先调用 setContentView()，然后找到 ImageView >:

setContentView(R.layout.my_layout)
this.imageView = (ImageView)findViewById(R.id.camera_thought);