Detailed explanation of Android events and gesture operations

Events and gestures

Event handling:

Physical event handling
Touch screen event handling
gesture

Physical event handling

Based on listening event processing
Callback event processing

Callback-based time processing: Rewrite Activity callback method

OnTouchEvent + OnKeyDown + OnKeyUp

Based on callback processing events, generalization is adopted. For example, in physical keys

1. Physical Events Provide three events:

Press: OnkeyDown, OnKeyUp: ONKeyLongPress(): Long press

Android provides keyword constants for each physical key in the middle: keyCODE_MENU,KEYCODE_HOME

Case: Press the return key twice in a row to return to the map

package ;
import ;
import ;
import ;
import ;
/**
  * Function: Press the return key twice in a row to exit the current application
  */
public class MainActivity extends AppCompatActivity {
    private long exitTime = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        (savedInstanceState);
        setContentView(.activity_main);
    }
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK){
            // Execute the exit method,            exit();
            return true;
        }
        return (keyCode, event);
    }
    public void exit() {
        if( (() - exitTime ) &gt; 2000){
            (, "Press again to exit the program", Toast.LENGTH_SHORT).show();
            exitTime = ();
        }else{
            finish();
            (0);
        }
    }
}

Touch Events

OnTouchEvent ()

package ;
import ;
import ;
import ;
import ;
import ;
/**
  * Features: Move hats with Touch to bring hats to penguins
  * 1. s instance top HatView in the figure shows the hat position
  * 2. Continuously update X,Y coordinates by listening to OnTouchEvent
  * 3. Put the hat layout manager, dynamic sky sword
  */
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        (savedInstanceState);
        setContentView(.activity_main);
        // Add a hat object and touch the event listener        final HatView hatView = new HatView();
        (new (){
            @Override
            public boolean onTouch(View view, MotionEvent motionEvent) {
                 = ()- 80; // Subtract the hat's normal height and move the center point                 = ();
                // New drawing                ();
                return true;
            }
        });
        RelativeLayout relativeLayout = findViewById();
        (hatView);
    }
}

package ;
import ;
import ;
import ;
import ;
import ;
import ;
/**
  * Hat Postition via Touch
  * */
public class HatView extends View {
    public float bitmapX;
    public float bitmapY;
    public HatView(Context context) {
        super(context);
         = 0.0f;
         = 0.0f;
    }
    /**
      * Repaint the hat
      * */
    @Override
    protected void onDraw(Canvas canvas) {
        (canvas);
        Paint paint = new Paint();
        Bitmap bitmap = ((), );
        (bitmap,bitmapX,bitmapY,paint);
        if(()){
            ();
        }
    }
}

Gesture detection

Provide a gesture detection

Gesture Listener must rewrite its six methods, onDown, OnFling (the user's finger drags through the touch screen), OnLongPress

OnScroll, onShowPress, onSingleTapUp (triggered by the user's finger on the screen)

Triggering function for instance users:

package ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
/**
   * Gesture mode sliding animation
  */
public class MainActivity extends AppCompatActivity implements  {
    ViewFlipper flipper; //Define ViewFlipper    GestureDetector detector; //Define gesture detector    Animation[] animation = new Animation[4];//Define an animation array and specify switching animations for ViewFlipper    final int distance = 50; //Define the minimum distance between two points of gesture action    //Define the image array    private int[] images = new int[]{.img01, .img02, .img03,
            .img04,
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        (savedInstanceState);
        setContentView(.activity_main);
        detector = new GestureDetector(, this);
        // Add the displayed animation to ViewFlipper and initialize the animation array        flipper = findViewById();
        for(int i= 0; i&lt; ; i++){
            ImageView imageView = new ImageView(this);
            (images[i]);
            (imageView);
        }
        // Load the animation resource component        animation[0] = (this, .slide_in_left);
        animation[1] = (this, .slide_out_left);
        animation[2] = (this, .slide_in_right);
        animation[3] = (this, .slide_out_right);
    }
    @Override
    public boolean onDown(MotionEvent motionEvent) {
        return false;
    }
    @Override
    public void onShowPress(MotionEvent motionEvent) {
    }
    @Override
    public boolean onSingleTapUp(MotionEvent motionEvent) {
        return false;
    }
    @Override
    public boolean onScroll(MotionEvent motionEvent, MotionEvent motionEvent1, float v, float v1) {
        return false;
    }
    @Override
    public void onLongPress(MotionEvent motionEvent) {
    }
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float v, float v1) {
        //Judge sliding trend by touching coordinates        if ((() - ()) &gt; distance){
            (animation[2]);
            (animation[1]);
            ();
            return  true;
        }else if (() - () &gt; distance) {
            // Set a switch animation for flipper            (animation[0]);
            (animation[3]);
            ();
            return true;
        }
        return false;
    }
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        return (event);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:andro
    xmlns:tools="/tools"
    android:
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">
    <ViewFlipper
        android:id = "@+id/flipper"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </ViewFlipper>
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:andro>
<translate
    android:fromXDelta="-100%p"
    android:toXDelta="0"
    android:duration="500"/>
</set>
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:andro>
    <translate
        android:duration="500"
        android:fromXDelta="100%p"
        android:toXDelta="0"/>

</set>
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:andro>
    <translate
        android:duration="500"
        android:fromXDelta="0"
        android:toXDelta="-100%p"/>
</set>
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:andro>
    <translate
        android:duration="500"
        android:fromXDelta="0"
        android:toXDelta="100%p"/>
</set>

Add gestures

Custom gestures:

Getsures Builder gesture app

Summarize:

1. GestureLibararias Load Custom Gesture Library

2. Get GestureOverlayView Set its event listener

3. All gesture predictions from GestureOverlayView are only obtained, and the maximum value is scored.

4. Add the original value from the edito edit box with the gesture of determining the highest value and will be written to the original edit box.

package ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
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import ;
import ;
/**
   * Gesture mode sliding animation
  */
public class MainActivity extends AppCompatActivity implements  {
    private GestureDetector detector;
    private GestureLibrary librarry;
    private EditText editText;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        (savedInstanceState);
        setContentView(.activity_main);
        // Load the custom gesture file, but exit without success        librarry = (, );
        editText = findViewById();
        if(!()){
            finish();
        }
        // Get GestureOverlayView Set its event listener        GestureOverlayView gestureOverlayView = findViewById();
        ();
        (1000);
        ();
    }
    @Override
    public void onGesturePerformed(GestureOverlayView gestureOverlayView, Gesture gesture) {
        // Get its best match and update the edit bar        ArrayList&lt;Prediction&gt; predictions = (gesture);
        int index = 0;// Save the index number of the current prediction        double score = 0.0;// Save the score of the current prediction        for (int i = 0; i &lt; (); i++) {// Get the best match result            Prediction result = (i);// Obtain a prediction result            if ( &gt; score) {
                index = i;
                score = ;
            }
        }
        String Text = ().toString();
        Text += (index).name;
        (Text);
    }
}

<?xml version="1.0" encoding="utf-8"?>

<EditText
    android:
    android:layout_width="200dp"
    android:layout_height="wrap_content"
    android:layout_marginLeft="40dp"
    android:layout_marginTop="190dp" />
<
    android:
    android:layout_width="320dp"
    android:layout_height="180dp"
    android:layout_alignParentBottom="true"
    android:layout_marginBottom="85dp"
    android:gestureStrokeType="multiple" />

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