public class MainActivity extends Activity {

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

        LinearLayout ll = new LinearLayout(this);
        ll.setOrientation(LinearLayout.VERTICAL);
        this.setContentView(ll);

        TextView tv = new TextView(this);
        tv.setText("Activity为: " + this.toString()
                + "\n" + ", Task ID 为:" + this.getTaskId());

        Button button = new Button(this);
        button.setText("启动Activity");
        ll.addView(tv);
        ll.addView(button);

        button.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent(MainActivity.this, MainActivity.class);
                        startActivity(intent);
                    }
                }
        );
    }

}

public class MainActivity extends Activity {

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

        LinearLayout ll = new LinearLayout(this);
        ll.setOrientation(LinearLayout.VERTICAL);
        this.setContentView(ll);

        TextView tv = new TextView(this);
        tv.setText("Activity为: " + this.toString()
                + "\n" + ", Task ID 为:" + this.getTaskId());

        Button button = new Button(this);
        button.setText("启动Activity");
        ll.addView(tv);
        ll.addView(button);

        button.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent(MainActivity.this, SecondActivity.class);
                        startActivity(intent);
                    }
                }
        );
    }
}

public class SecondActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        LinearLayout ll = new LinearLayout(this);
        ll.setOrientation(LinearLayout.VERTICAL);
        this.setContentView(ll);

        TextView tv = new TextView(this);
        tv.setText("Activity为: " + this.toString()
                + "\n" + ", Task ID 为:" + this.getTaskId());

        Button button = new Button(this);
        button.setText("启动Activity");
        ll.addView(tv);
        ll.addView(button);

        button.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent(SecondActivity.this,MainActivity.class);
                        startActivity(intent);
                    }
                }
        );
    }
}

public class MainActivity extends Activity {

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

        LinearLayout ll = new LinearLayout(this);
        ll.setOrientation(LinearLayout.VERTICAL);
        this.setContentView(ll);

        TextView tv = new TextView(this);
        tv.setText("Activity为: " + this.toString()
                + "\n" + ", Task ID 为:" + this.getTaskId());

        Button button = new Button(this);
        button.setText("启动Activity");
        ll.addView(tv);
        ll.addView(button);

        button.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent(MainActivity.this, SecondActivity.class);
                        startActivity(intent);
                    }
                }
        );
    }
}

public class SecondActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        LinearLayout ll = new LinearLayout(this);
        ll.setOrientation(LinearLayout.VERTICAL);
        this.setContentView(ll);

        TextView tv = new TextView(this);
        tv.setText("Activity为: " + this.toString()
                + "\n" + ", Task ID 为:" + this.getTaskId());

        Button button = new Button(this);
        button.setText("启动Activity");
        ll.addView(tv);
        ll.addView(button);

        button.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent();
                        intent.setAction("org.crazyit.intent.action.CRAZYIT_ACTION");
                        startActivity(intent);
                    }
                }
        );
    }
}

 <activity
            android:name="com.example.dada.testapplication.SecondActivity"
            android:launchMode="singleInstance"
            android:exported="true"
            android:label="@string/title_activity_second" >
            <intent-filter>
                <action android:name="org.crazyit.intent.action.CRAZYIT_ACTION" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>