控制畫面的Activity

The onCreate(Bundle) method is called when an instance of the activity subclass is created. 'When an activity is created, it needs a user interface to manage.
To get the activity its user interface, you call the following Activity method:
    public void setContentView(int layoutResID)

ex:

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
}

說明:
setContentView: 設定連結layout的resource ID

設定layout上widget的resource ID:
(只有需要控制的才需設定)

利用android:id="@+id/名稱"

ex:

activity_main.xml:


 <Button
        android:id="@+id/true_button"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="@string/true_button" />

    <Button
      android:id="@+id/false_button"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="@string/false_button" />

->

R.java:


public static final class id {
        public static final int action_settings=0x7f080002;
        public static final int false_button=0x7f080001;
        public static final int true_button=0x7f080000;
    }


從程式存取XML裡設定的widget:
利用resource id找到widget


        Button mTrueButton = (Button)findViewById(R.id.true_button);

建立activity和顯示activity的流程:

1. 新增activity的類別 (.java檔)
2. 新增activity對應的layout (.xml檔)
3. 設計activity的layout ( .xml 檔)
4. 於activity的java檔連結xml
ex:

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_period);
       
    }

5. 於AndroidManifest.xml加入activity
ex:

  <activity
            android:name=".AddPeriodActivity"
            android:label="@string/app_name" >
         
        </activity>

6. 顯示activity
ex:

   Intent intent = new Intent(this, AddPeriodActivity.class);
   this.startActivity(intent);