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

Question

I'm new to android and I'm trying to implement MyFirstApp given on android google developers site, So app contains one textbox and button, if you enter any text in textfield and click on button it displays same content on screen, but having problem when i clicked on send button. Please guide me how to solve this problem.

Following exceptions:

<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>

Here are two activities:
1.DisplayMessageActivity this is activity mentioned in android manifest file . This implement layout part

       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
this is activity implement sendmessage function that is called when users clicked on button .

      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 file:

<?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>

And Layout xml file:

 <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

Edit:

Change your Manifest:

<?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>

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);



    }
       }

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);
    }

}

---

your layout should have a life cycle method onCreate It should have a onCreate method and you need to set setContentview(R.layout.yourlayout) for the MainActivity

Answer 2

Your app is looking for the sendMessage() method in an activity where the method is not implimented

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): 

is this the xml layout name activity_display_message_1 where you declare the Button? you must put the method sendMessage also in the same activity

EDIT: FULL SOLUTION

activity_main.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" >
    <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);
}

}

Update also you manifest file because you've inverse the launcher

<?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

You are using two time setContentView() . You can use only one setContentView .

Answer 4

//Just change your manifest file, its not getting path of your "DisplayMessageActivity" for //sample as below :

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

or

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);
}