Save data to deal with auto-rotate

SaveDataToDealWithAutoRotate.java

/**
 * All activity data would be destoryed after the device rotate
 * So we need save the data first and recall it after the device rotate
 */

 public class MainActiviy extends AppCompatActivity {
     // example key variable
     private static final String KEY_INDEX = "index";

     // example data variable
     private static final int mData;

     @Override
     public void onCreate (Bundle saveInstanceState) {
         super.onCreate(saveInstanceState);

         // recall the variable
         if (saveInstanceState != null) {
             // get the data
             mData = saveInstanceState.getInt(KEY_INDEX, 0);
         }

        // do something with data...
     }

    /**
     * save the data before device rotate
     */
     @Override
     public void onSaveInstanceState(Bundle saveInstanceState) {
         super.onSaveInstanceState(saveInstanceState);
         saveInstanceState.putInt(KEY_INDEX, mData);
     }
 }