I'm feeling stupid.This is very clear but I can not solve my problem.So excuse me for my question.  

My problem is in about intenfilter.This is application tag of my manifest file: 

```
<application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:label="@string/app_name"
            android:name=".AlakyTestActivity" >
            <intent-filter >
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:label="reza"
            android:name=".A2" >
            <intent-filter >
                <action android:name="MAIN" />

                <category android:name="LAUNCHER" />
            </intent-filter>
        </activity>
    </application>     

```

And this is my button click listener: 

```
b1 = (Button)findViewById(R.id.button1);
        b1.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                Intent intent2 = new Intent();
                intent2.setAction("MAIN");
                intent2.addCategory("LAUNCHER");
                startActivity(intent2);
            }
        });      

```

I think that all things is good but when I run my code and click on `b1`,I get this erroe: 

```
android.content.ActivityNotFoundException: No Activity found to handle Intent { act=MAIN cat=[LAUNCHER] }      

```

**Edit**:  

This is A2: 

```
public class A2 extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        this.setContentView(R.layout.main2);
    }

}

```

Please help me.