Question

我是Android的新手，我正在尝试在Android google开发者网站上实现MyFirstApp，所以app包含一个文本框和按钮，如果你在textfield中输入任何文本并点击按钮它会在屏幕上显示相同的内容，但是当我点击发送按钮时出现问题。请指导我如何解决这个问题。

以下例外情况：

<p>03-15 18:00:03.430: E/AndroidRuntime(592): FATAL EXCEPTION: main</p>
<p>03-15 18:00:03.430: E/AndroidRuntime(592): java.lang.IllegalStateException:Could not find a method MainActivity.sendMessage(View) in the activity class com.example.myfirstapp.DisplayMessageActivity for onClick handler on view class android.widget.Button</p>
<p>03-15 18:00:03.430: E/AndroidRuntime(592):   at android.view.View$1.onClick(View.java:3031)</p>
<p>03-15 18:00:03.430: E/AndroidRuntime(592):   at android.view.View.performClick(View.java:3511)</p>

以下是两项活动：
1.DisplayMessageActivity 这是android清单文件中提到的活动。这个工具布局部分

       public class DisplayMessageActivity extends Activity {

        @Override
         protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);



        // Get the message from the intent
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

        // Create the text view
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

        // Set the text view as the activity layout
        setContentView(textView);

        setContentView(R.layout.activity_display_message_1);

    }
       }

2.MainActivity
这是用户点击按钮时调用的活动实现sendmessage函数。

      public class MainActivity extends Activity {

    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";

    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        // Do something in response to button
        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);
    }


}

Android Manifest xml文件：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myfirstapp"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="11" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="DisplayMessageActivity"
            android:label="@string/title_activity_display_message">
           <intent-filter >
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter> 
        </activity>
    </application>

</manifest>

和布局xml文件：

 <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" >

    <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>

Answer 1

修改

更改您的舱单：

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.myfirstapp" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="11" /> <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name=".MainActivity" android:label="@string/title_activity_display_message"> <intent-filter > <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name=".DisplayMessageActivity" /> </application> </manifest>

<强> DisplayMessgaeActivity ：

public class DisplayMessageActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Get the message from the intent Intent intent = getIntent(); String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE); // Create the text view TextView textView = new TextView(this); textView.setTextSize(40); textView.setText(message); // Set the text view as the activity layout setContentView(textView); } }

<强> MainActivity ：

public class MainActivity 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_display_message_1); } /** Called when the user clicks the Send button */ public void sendMessage() { // Do something in response to button 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); } }

你的布局应该有一个生命周期方法onCreate 它应该有一个onCreate方法，你需要设置 MainActivity的setContentview(R.layout.yourlayout)

Answer 2

您的应用正在寻找方法未被激活的活动中的sendMessage()方法

java.lang.IllegalStateException:Could not find a method MainActivity.sendMessage(View) in the activity class com.example.myfirstapp.DisplayMessageActivity for onClick handler on view class android.widget.Button</p>
<p>03-15 18:00:03.430: E/AndroidRuntime(592):

这是你声明Button的xml布局名activity_display_message_1吗？您必须将方法sendMessage也放在同一个活动中

编辑：完整的解决方案

activity_main.xml中

 <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" >
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send"
        android:onClick="sendMessage" />
</LinearLayout>

activity_display_message.xml

<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" >

    <EditText android:id="@+id/edit_message"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/edit_message" />
</LinearLayout>

MainActivity

public class MainActivity 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);
}


    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        // Do something in response to button
        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);
    }
}

DisplayMessageActivity.java

  public class DisplayMessageActivity extends Activity {

    @Override
     protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_display_message_1);


    // Get the message from the intent
    Intent intent = getIntent();
    String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

    // Create the text view
    TextView textView = new TextView(this);
    textView.setTextSize(40);
    textView.setText(message);
}

}

更新你清单文件，因为你已经反转了启动器

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myfirstapp"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="11" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
 <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_display_message">
           <intent-filter >
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter> 
        </activity>


<activity
            android:name=".DisplayMessageActivity" />
    </application>

</manifest>

Answer 3

您正在使用两次setContentView()。您只能使用一个setContentView。

Answer 4

//只需更改您的清单文件，不要获取//示例的“DisplayMessageActivity”路径，如下所示：

 android:name="com.example.checkproject.DisplayMessageActivity"

或

android:name =".DisplayMessageActivity"

Answer 5

public void sendMessage(View view) {
    // Do something in response to button
    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);
    this.startActivity(intent);
}

单击android hello world程序中的按钮时出现IllegalStateException

5 个答案: