Android 从firebase中删除项目而不使应用程序崩溃
我是android新手,我一直在玩firebase的示例应用程序。我想添加一个delete按钮,通过将DatabaseReference mPostReference设置为null,从数据库中删除当前正在查看的帖子。但是,这会导致添加到MPosReference的ValueEventListener出现空指针异常,从而导致应用程序崩溃Android 从firebase中删除项目而不使应用程序崩溃,android,firebase,firebase-realtime-database,Android,Firebase,Firebase Realtime Database,我是android新手,我一直在玩firebase的示例应用程序。我想添加一个delete按钮,通过将DatabaseReference mPostReference设置为null,从数据库中删除当前正在查看的帖子。但是,这会导致添加到MPosReference的ValueEventListener出现空指针异常,从而导致应用程序崩溃 // Get post key from intent mPostKey = getIntent().getStringExtra(EXTRA_P
// Get post key from intent
mPostKey = getIntent().getStringExtra(EXTRA_POST_KEY);
if (mPostKey == null) {
throw new IllegalArgumentException("Must pass EXTRA_POST_KEY");
}
// Initialize Database
mPostReference = FirebaseDatabase.getInstance().getReference()
.child("posts").child(mPostKey);
ValueEventListener postListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// Get Post object and use the values to update the UI
Post post = dataSnapshot.getValue(Post.class);
// Text Views in activity
mAuthorView.setText(post.author);
mTitleView.setText(post.title);
mBodyView.setText(post.body);
}
@Override
public void onCancelled(DatabaseError databaseError) {
// Getting Post failed, log a message
Log.w(TAG, "loadPost:onCancelled", databaseError.toException());
// [START_EXCLUDE]
Toast.makeText(PostDetailActivity.this, "Failed to load post.",
Toast.LENGTH_SHORT).show();
// [END_EXCLUDE]
}
};
mPostReference.addValueEventListener(postListener);
//delete button clicked
deleteButton.setOnClickListener(new View.OnClickListener() {
mPostReference.setValue(null);
}
如果mpostreeference已被删除或设置为null,是否有办法防止应用程序崩溃?是否有更好的方法实现删除按钮?
如有任何想法/建议,将不胜感激。多谢各位
这是日志
FATAL EXCEPTION: main
Process: com.google.firebase.quickstart.database, PID: 2861
java.lang.NullPointerException: Attempt to read from field 'java.lang.String com.google.firebase.quickstart.database.models.Post.author' on a null object reference
at com.google.firebase.quickstart.database.PostDetailActivity$1.onDataChange(PostDetailActivity.java:93)
at com.google.android.gms.internal.zzbmz.zza(Unknown Source)
at com.google.android.gms.internal.zzbnz.zzYj(Unknown Source)
at com.google.android.gms.internal.zzboc$1.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6145)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
您只需要添加一个
if
语句来检查dataSnapshot
是否有值或null
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
// Get Post object and use the values to update the UI
Post post = dataSnapshot.getValue(Post.class);
// Text Views in activity
mAuthorView.setText(post.author);
mTitleView.setText(post.title);
mBodyView.setText(post.body);
}
}
请提供logcatoutput@AdityaK添加了logcat输出:)