android 鍵盤事件和屏幕事件的運行原理及交互實現

當在自定義View或者做游戲的時候，我們常常會用到鍵盤觸發事件和屏幕觸發事件！在自定義的View裡的鍵盤觸發事件（比如：onKeyDown(int keyCode, KeyEvent event)）和屏幕觸發事件（onTouchEvent(MotionEvent event)）和activity裡的鍵盤觸發事件（比如：onKeyDown(int keyCode, KeyEvent event)）和屏幕觸發事件（onTouchEvent(MotionEvent event)）是怎麼樣交互的呢？是怎樣的一個運行原理呢？下面來看看：

1、屏幕觸發事件：哪個activity或者視圖，控件在最上層就最先觸發這個控件裡的屏幕觸發事件，返回值如果是默認或者false就會一層一層的往下傳遞！如果返回值是true,則在執行完動作之後不會往下傳遞！
2、鍵盤觸發事件：這個原理和屏幕觸發事件差不多，但是不同的時，在沒有設置控件處於焦點時，一般按鍵盤裡的按鍵觸發的是activity裡的鍵盤觸發事件（比如：onKeyDown(int keyCode, KeyEvent event)）。

下面來舉個例子：
比如在做游戲的時候，我們經常自定義視圖，我們一般都喜歡和使用觸發本視圖（GameView）裡的鍵盤觸發事件和屏幕觸發事件，但是比如：onKeyDown(int keyCode, KeyEvent event）)，一般我們按鍵盤的時候直接觸發的是activity裡的鍵盤觸發事件，怎樣讓它直接觸發（GameView）裡的鍵盤觸發事件呢?

第一種方法：
例子1：
代碼如下：

View Code
package net.loonggg.project;
import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.MotionEvent;
public class MainActivity extends Activity {
private GameView gameView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
gameView = new GameView(this);
setContentView(gameView);
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
System.out.println("MainActivity:" + " keyCode:" + keyCode + " evnet:"
+ event);
return super.onKeyDown(keyCode, event);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
System.out.println("MainActivity:" + " event:" + event + " x:"
+ event.getX() + " y:" + event.getY());
return super.onTouchEvent(event);
}
}
package net.loonggg.project;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
public class GameView extends View {
private Paint paint;
private int pointX;
private int pointY;
public GameView(Context context) {
super(context);
// 設置GameView獲得焦點
this.setFocusable(true);
paint = new Paint();
paint.setColor(Color.YELLOW);
Thread t = new Thread(new MyThread());
t.start();
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawCircle(pointX, pointY, 15, paint);
}
class MyThread implements Runnable {
@Override
public void run() {
while (true) {
try {
Thread.sleep(3000);
pointY = pointY + 10;
pointX = pointX + 10;
if (pointX > 200) {
break;
}
} catch (InterruptedException e) {
e.printStackTrace();
}
GameView.this.postInvalidate();
}
}
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
System.out.println("GameView:" + " keyCode:" + keyCode + " evnet:"
+ event);
//此事件不會傳播出去
return true;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
System.out.println("GameView:" + " event:" + event + " x:"
+ event.getX() + " y:" + event.getY());
//此事件不會傳播出去
return true;
}
}

第二種方法：
代碼如下：

View Code
package net.loonggg.project;
import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.MotionEvent;
public class MainActivity extends Activity {
private GameView gameView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
gameView = new GameView(this);
setContentView(gameView);
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
System.out.println("MainActivity:" + " keyCode:" + keyCode + " evnet:"
+ event);
//把事件傳遞給gameView
gameView.onKeyDown(keyCode, event);
return super.onKeyDown(keyCode, event);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
System.out.println("MainActivity:" + " event:" + event + " x:"
+ event.getX() + " y:" + event.getY());
//把事件傳遞給gameView
gameView.onTouchEvent(event);
return super.onTouchEvent(event);
}
}
package net.loonggg.project;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
public class GameView extends View {
private Paint paint;
private int pointX;
private int pointY;
public GameView(Context context) {
super(context);
paint = new Paint();
paint.setColor(Color.YELLOW);
Thread t = new Thread(new MyThread());
t.start();
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawCircle(pointX, pointY, 15, paint);
}
class MyThread implements Runnable {
@Override
public void run() {
while (true) {
try {
Thread.sleep(3000);
pointY = pointY + 10;
pointX = pointX + 10;
if (pointX > 200) {
break;
}
} catch (InterruptedException e) {
e.printStackTrace();
}
GameView.this.postInvalidate();
}
}
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
System.out.println("GameView:" + " keyCode:" + keyCode + " evnet:"
+ event);
return super.onKeyDown(keyCode, event);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
System.out.println("GameView:" + " event:" + event + " x:"
+ event.getX() + " y:" + event.getY());
return super.onTouchEvent(event);
}
}

在這裡，推薦使用第二種方法，因為第一種方法有的模擬器不能夠使用！
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