java.lang.IllegalStateException:找不到sendMessage(View)方法

Question

java code:

package com.example.myfirstapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.widget.EditText;
public class MainActivity<View> extends Activity {
    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

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

activity_main.xml:

<?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>

错误信息:

06-18 15:19:12.493: E/AndroidRuntime(799): 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

我真的不知道原因，我检查了关于方法名的情况，没关系。谁能帮我?

Answer 1

你必须声明你的活动为:

public class MainActivity extends Activity {
}

，你还需要在你的onCreate()方法声明你的按钮，如下所示:

Button button_send= (Button)findViewById(R.id.your_Button_Id);

更新:

你还必须在清单中为你的按钮分配一个id，并在上面参考它。

Answer 2

删除<View>。还要将Editext的初始化移到oncreate()。无需每次点击按钮时都初始化编辑文本。

public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
private EdiText editext; 
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    editText = (EditText) findViewById(R.id.edit_message); 
} 
....