当按下按钮时，应用崩溃

Question

I am trying to run an app and when I try to tap the button the app crashes when it is supposed to save data for backup

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.back4app.userregistrationexample, PID: 31963
java.lang.IllegalStateException: Could not find method onclick(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatButton with id 'btn_addbalance'
            at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.resolveMethod(AppCompatViewInflater.java:423)
            at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:380)
            at android.view.View.performClick(View.java:6329)
            at android.view.View$PerformClick.run(View.java:25002)
            at android.os.Handler.handleCallback(Handler.java:809)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:166)
            at android.app.ActivityThread.main(ActivityThread.java:7555)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:469)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:963)
        I/Process: Sending signal. PID: 31963 SIG: 9
        Application terminated.

Here in the balance I only put the code that I think is needed but if the whole class is needed I will edit it too
Balance

@Override
 public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.app_bar_balance);
                Parse.initialize(new Parse.Configuration.Builder(this)
                        .applicationId("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")
                        .clientKey("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")
                        .server("https://parseapi.back4app.com/").build()
                );
                LiveQueryClient.init("wss://" + "aaaa.back4app.io", "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", true); // Example: 'wss://livequerytutorial.back4app.io'
                LiveQueryClient.connect();

                Balance = (EditText) findViewById(R.id.txt_editbalance);

                final Button addbalance = findViewById(R.id.btn_addbalance);
                addbalance.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        //Validating the log in data
                        boolean validationError = false;

                        StringBuilder validationErrorMessage = new StringBuilder("Please, insert ");
                        if (isEmpty(Balance)) {
                            validationError = true;
                            validationErrorMessage.append("an balance");
                        }
                        validationErrorMessage.append(".");

                        if (validationError) {
                            Toast.makeText(Balance.this, validationErrorMessage.toString(), Toast.LENGTH_LONG).show();
                            return;
                        }
                        //Setting up a progress dialog
                        final ProgressDialog dlg = new ProgressDialog(Balance.this);
                        dlg.setTitle("Please, wait a moment.");
                        dlg.setMessage("Adding Load...");
                        dlg.show();

                        ParseUser balance = new ParseUser();
                        balance.setUsername(Balance.getText().toString());
                        balance.signUpInBackground(new SignUpCallback() {
                            @Override
                            public void done(ParseException e) {
                                if (e == null) {
                                    dlg.dismiss();

                                } else {
                                    dlg.dismiss();
                                    ParseUser.logOut();
                                    Toast.makeText(Balance.this, e.getMessage(), Toast.LENGTH_LONG).show();
                                }
                            }
                        });

                    }
                });
            }

I tried to change the names switching it back and forth hoping that it might fix the problem app bar balance

        <?xml version="1.0" encoding="utf-8"?>
        <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent" android:layout_height="match_parent">

        <TextView
            android:id="@+id/txt_currentbal"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="59dp"
            android:text="Current Balance" />

        <TextView
            android:id="@+id/txt_balance"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="96dp"
            android:text="android:id" />

        <TextView
            android:id="@+id/txt_addbal"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="185dp"
            android:text="Add Balance" />

        <EditText
            android:id="@+id/txt_editbalance"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="230dp"
            android:ems="10"
            android:hint="Add Balance"
            android:inputType="number" />

        <Button
            android:id="@+id/btn_addbalance"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_centerHorizontal="true"
            android:layout_marginBottom="177dp"
            android:onClick="onclick"
            android:text="Add Balance" />
    </RelativeLayout>

Now I removed the android:onClick="onclick" and now it looks like this but when I run it again on my phone now it doesn't do anything and the run doesn't even respond when the button is pressed

Answer 1

You already set ClickListener from your from your code. So button onClick attribute not needed.

Just remove this line from the Button.

android:onClick="onclick"

It will look like this

<Button
    android:id="@+id/btn_addbalance"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="177dp"
    android:text="Add Balance" />

This will solve your problem.

Answer 2

In your XML you use a button from the support library (widget.AppCompatButton), but in your code you're trying to cast it to a regular Button. Either use the regular Button in your XML code, or use the AppCompatButton in the Java code.

Seeing that you are using the support library (you're using the AppCompatActivity), I'd advice you to change 'Button' to 'AppCompatButton' in your Java code.

Answer 3

将onclick（）方法放在xml的按钮视图中

Answer 4

If you want to use in XML onClick then use like this :

<Button
    android:id="@+id/btn_addbalance"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="177dp"
    android:onClick="onClick"
    android:text="Add Balance" />

you have entered in wrong format

do this : "onClick"

instead of : "onclick "

you can check in logcats it's shows also same thing in it, So change it :

Could not find method onclick(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatButton with id 'btn_addbalance'

by the way there is no need to add attribute in xml if you are doing in java