Question

我目前正在努力获得Android的基本My First App教程（由谷歌创建），但我遇到了一些问题。目前应用程序如何在Eclipse中显示错误，但是当我运行应用程序并单击“发送”按钮时，应用程序崩溃显示Unfortunately, My First App has stopped.

在Log cat中查找错误，指出

java.lang.IllegalStateException: Could not find a method sendMessage(View) 
in the activity class com.example.myfirstapp.MainActivity for onClick handler 
on view class android.widget.Button.

sendMessage确实存在于MainActivity类中，但它是函数PlaceholderFragment中的嵌套类。最初我认为这是一个索引错误，因此我尝试像嵌套类sendMessage一样调用android:onClick="PlaceholderFragment.sendMessage"但没有成功。我已经包含了fragment_main和MainActivity类以及我的完整logcat错误。谢谢你的帮助。

MainActivity：

package com.example.myfirstapp;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;



public class MainActivity extends ActionBarActivity {
    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";   

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment())
                    .commit();
        }
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
           return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
    * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            return rootView;
        }
        /** Called when the user clicks the Send button */
        public void sendMessage(View view) {
            Intent intent = new Intent(getActivity(), DisplayMessageActivity.class);
            EditText editText = (EditText)getActivity(). findViewById(R.id.edit_message);
            String message = editText.getText().toString();
            intent.putExtra(EXTRA_MESSAGE, message);
            startActivity(intent);
        }

    }

}

Fragment Main：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">
    <EditText android:id="@+id/edit_message"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/edit_message" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send"
        android:onClick="sendMessage" />
</LinearLayout>

logcat的：

04-25 12:04:07.220: D/(1274): HostConnection::get() New Host Connection established 0xb8e4f238, tid 1274
04-25 12:04:07.330: W/EGL_emulation(1274): eglSurfaceAttrib not implemented
04-25 12:04:07.340: D/OpenGLRenderer(1274): Enabling debug mode 0
04-25 12:04:10.620: D/AndroidRuntime(1274): Shutting down VM
04-25 12:04:10.620: W/dalvikvm(1274): threadid=1: thread exiting with uncaught exception (group=0xb2a6bba8)
04-25 12:04:10.750: E/AndroidRuntime(1274): FATAL EXCEPTION: main
04-25 12:04:10.750: E/AndroidRuntime(1274): Process: com.example.myfirstapp, PID: 1274
04-25 12:04:10.750: E/AndroidRuntime(1274): java.lang.IllegalStateException: Could not find a method sendMessage(View) in the activity class com.example.myfirstapp.MainActivity for onClick handler on view class android.widget.Button
04-25 12:04:10.750: E/AndroidRuntime(1274):     at android.view.View$1.onClick(View.java:3810)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at android.view.View.performClick(View.java:4438)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at     android.view.View$PerformClick.run(View.java:18422)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at android.os.Handler.handleCallback(Handler.java:733)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at android.os.Handler.dispatchMessage(Handler.java:95)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at android.os.Looper.loop(Looper.java:136)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at android.app.ActivityThread.main(ActivityThread.java:5017)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at java.lang.reflect.Method.invokeNative(Native Method)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at java.lang.reflect.Method.invoke(Method.java:515)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at dalvik.system.NativeStart.main(Native Method)
04-25 12:04:10.750: E/AndroidRuntime(1274): Caused by: java.lang.NoSuchMethodException: sendMessage [class android.view.View]
04-25 12:04:10.750: E/AndroidRuntime(1274):     at java.lang.Class.getConstructorOrMethod(Class.java:472)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at java.lang.Class.getMethod(Class.java:857)
04-25 12:04:10.750: E/AndroidRuntime(1274):     at android.view.View$1.onClick(View.java:3803)
04-25 12:04:10.750: E/AndroidRuntime(1274):     ... 11 more
04-25 12:04:12.720: I/Process(1274): Sending signal. PID: 1274 SIG: 9

Answer 1

看起来你的问题是sendMessage函数应该包含在你的MainActivity中而不是嵌套在你的片段中。

调试行：

java.lang.IllegalStateException: Could not find a method sendMessage(View) in the activity class com.example.myfirstapp.MainActivity for onClick handler on view class android.widget.Button

显示应用程序正在您的MainActivity类中查找此方法。

Answer 2

将sendMessage(View view)方法放在MainActivity类而不是PlaceholderFragment类

中

Answer 3

从xml处理clicklistener并不总是一个好主意。在按钮的片段中设置clicklistener，并从clicklistener的sendMessage方法调用onClick方法。

首先为您的按钮设置ID（例如：sendButton）。

然后，

public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        Button b = (Button) rootView.findViewByID(R.id.sendButton);
        //Here set the clickListener and call sendMessage method
        return rootView;
    }


    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        Intent intent = new Intent(getActivity(), DisplayMessageActivity.class);
        EditText editText = (EditText)getActivity(). findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
    }

}

或者在片段中实现View.OnClickListener然后有一个case语句，如：

@Override
public void onClick(View view) {
    switch (view.getId()) {
        case R.id.sendButton:
            sendMessage();
            break;
        default:
            Log.i(TAG, "Unknown: " + view.getId());
            break;
    }
}

Answer 4

以编程方式执行：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        Button b = (Button) rootView.findViewById(R.id.my_button);
        b.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // handle click here
            }
        });
        return rootView;
}

并将其插入主活动布局的Button部分：机器人：ID = “@ + ID / my_button”

Answer 5

机器人：的onClick =＆＃34;的sendMessage＆＃34;

按钮onClick属性搜索Activity中的相应方法。但是你在Fragment中定义了这个方法，这就是你获得异常的原因方法找不到异常。

Android推荐的方法来处理片段内的onClick for按钮首先将ID分配给按钮

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<EditText android:id="@+id/edit_message"
    android:layout_weight="1"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:hint="@string/edit_message" />
<Button
    android:id="@+id/button1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/button_send"
     />
   </LinearLayout>

你的Fragment然后用onClick监听器注册按钮

/**
* A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment  implements OnItemClickListener{

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
     Button b = (Button) rootView.findViewById(R.id.button1);
    b.setOnClickListener(this);
        return rootView;
    }
    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        Intent intent = new Intent(getActivity(), DisplayMessageActivity.class);
        EditText editText = (EditText)getActivity(). findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
    }

    public void onClick(View view)
    {
       sendMessage(view);
    }
}

Android我的第一个应用程序教程android：onClick问题

5 个答案: