android之DPAD上下左右四个键控制

我们代码的目的很简单，那就是监听上下左右中这几个键的事件触发。直接上代码：

dpad.xml

<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:background="#FFFFFF"
  >
  <Button
    android:id="@+id/myButton1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="move me"
    android:layout_x="20px"
    android:layout_y="40px" />
</AbsoluteLayout>

<?xml version="1.0" encoding="utf-8"?> <AbsoluteLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="#FFFFFF" > <Button android:id="@+id/myButton1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="move me" android:layout_x="20px" android:layout_y="40px" /> </AbsoluteLayout>

activity代码：

package cn.com.chenzheng_java;

import android.app.Activity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.KeyEvent;
import android.widget.AbsoluteLayout;
import android.widget.Button;
import android.widget.Toast;
/**
 * @description 控制手机的上下左右四个方向键
 * @author chenzheng_java
 *
 */
public class DpadActivity extends Activity {
    Button button;
    DisplayMetrics metrics = new DisplayMetrics();
    int screenx = 0 ;//屏幕宽度
    int screeny = 0 ;//屏幕高度
    int buttonWidth = 80;//按钮宽度
    int buttonHeight = 40 ;// 按钮高度
    int currentX = 0;// 按钮的当前x坐标
    int currentY = 0;// 按钮的当前Y坐标
    int step = 0;//移动时候的步长
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.dpad);
        button = (Button) findViewById(R.id.myButton1);
        getWindowManager().getDefaultDisplay().getMetrics(metrics);
        screenx = metrics.widthPixels;
        screeny = metrics.heightPixels;
    /*  buttonWidth = button.getWidth();
        buttonHeight = button.getHeight();*/

        currentX = (screenx-buttonWidth)/2;
        currentY = (screeny-buttonHeight)/2;
        step = 2;

        button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY));

    }

    /**
     * 当前后左右键被按下的时候，被触发(这里可是有前提的哦，那就是当前的activity中必须没有view正在监听按键
     * ，例如：当前如果有一个EditText正在等待输入，当我们按下dpad时，不会触发事件哦)
     * Activity.onKeyDown();
当某个键被按下时会触发，但不会被任何的该Activity内的任何view处理。
默认按下KEYCODE_BACK键后会回到上一个Activity。
     */
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        switch (keyCode) {
        case KeyEvent.KEYCODE_DPAD_DOWN://按向下键
            moveDown();
            break;
        case KeyEvent.KEYCODE_DPAD_UP:// 按向上键
            moveUp();
        case KeyEvent.KEYCODE_DPAD_LEFT://按向左键
            moveLeft();
        case KeyEvent.KEYCODE_DPAD_RIGHT://按向右键
            moveRight();
        default:
            break;
        }

        return super.onKeyDown(keyCode, event);
    }


    @SuppressWarnings("deprecation")
    private void moveDown(){
        int temp = currentY+step;
        if(temp>(screeny-buttonHeight)){
            showToast("到头了哦！");
            button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, screenx, screeny-buttonHeight));
        }
        else{
            currentY = currentY+step;
            AbsoluteLayout.LayoutParams params =
                new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY);
            button.setLayoutParams(params);

        }
    //button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY-2));


    }

    @SuppressWarnings("deprecation")
    private void moveUp(){
        int temp = currentY-step;
        if(temp<=0){
            showToast("往上到头了哦！");
            button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, screenx, 0));
        }
        else{
            currentY = currentY-step;
            AbsoluteLayout.LayoutParams params =
                new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY);
            button.setLayoutParams(params);
        }


    }

    @SuppressWarnings("deprecation")
    private void moveLeft(){
        int temp = currentX-step;
        if(temp<=0){
            showToast("往左边到头了哦！");
            button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, 0, screeny));
        }
        else{
            currentX = currentX-step;
            AbsoluteLayout.LayoutParams params =
                new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY);
            button.setLayoutParams(params);
        }


    }

    @SuppressWarnings("deprecation")
    private void moveRight(){
        int temp = currentX+step;
        if(temp>=(screenx-buttonWidth)){
            showToast("往右边到头了哦！");
            button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, screenx-buttonWidth, currentY));
        }
        else{
            currentX = currentX+step;
            AbsoluteLayout.LayoutParams params =
                new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY);
            button.setLayoutParams(params);
        }


    }

    /**
     * 弹出提示信息
     * @param text 提示信息
     */
    private void showToast(String text){
        Toast.makeText(this, text, Toast.LENGTH_LONG).show();

    }

}

package cn.com.chenzheng_java; import android.app.Activity; import android.os.Bundle; import android.util.DisplayMetrics; import android.view.KeyEvent; import android.widget.AbsoluteLayout; import android.widget.Button; import android.widget.Toast; /** * @description 控制手机的上下左右四个方向键 * @author chenzheng_java * */ public class DpadActivity extends Activity { Button button; DisplayMetrics metrics = new DisplayMetrics(); int screenx = 0 ;//屏幕宽度 int screeny = 0 ;//屏幕高度 int buttonWidth = 80;//按钮宽度 int buttonHeight = 40 ;// 按钮高度 int currentX = 0;// 按钮的当前x坐标 int currentY = 0;// 按钮的当前Y坐标 int step = 0;//移动时候的步长 @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.dpad); button = (Button) findViewById(R.id.myButton1); getWindowManager().getDefaultDisplay().getMetrics(metrics); screenx = metrics.widthPixels; screeny = metrics.heightPixels; /* buttonWidth = button.getWidth(); buttonHeight = button.getHeight();*/ currentX = (screenx-buttonWidth)/2; currentY = (screeny-buttonHeight)/2; step = 2; button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY)); } /** * 当前后左右键被按下的时候，被触发(这里可是有前提的哦，那就是当前的activity中必须没有view正在监听按键 * ，例如：当前如果有一个EditText正在等待输入，当我们按下dpad时，不会触发事件哦) * Activity.onKeyDown(); 当某个键被按下时会触发，但不会被任何的该Activity内的任何view处理。 默认按下KEYCODE_BACK键后会回到上一个Activity。 */ @Override public boolean onKeyDown(int keyCode, KeyEvent event) { switch (keyCode) { case KeyEvent.KEYCODE_DPAD_DOWN://按向下键 moveDown(); break; case KeyEvent.KEYCODE_DPAD_UP:// 按向上键 moveUp(); case KeyEvent.KEYCODE_DPAD_LEFT://按向左键 moveLeft(); case KeyEvent.KEYCODE_DPAD_RIGHT://按向右键 moveRight(); default: break; } return super.onKeyDown(keyCode, event); } @SuppressWarnings("deprecation") private void moveDown(){ int temp = currentY+step; if(temp>(screeny-buttonHeight)){ showToast("到头了哦！"); button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, screenx, screeny-buttonHeight)); } else{ currentY = currentY+step; AbsoluteLayout.LayoutParams params = new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY); button.setLayoutParams(params); } //button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY-2)); } @SuppressWarnings("deprecation") private void moveUp(){ int temp = currentY-step; if(temp<=0){ showToast("往上到头了哦！"); button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, screenx, 0)); } else{ currentY = currentY-step; AbsoluteLayout.LayoutParams params = new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY); button.setLayoutParams(params); } } @SuppressWarnings("deprecation") private void moveLeft(){ int temp = currentX-step; if(temp<=0){ showToast("往左边到头了哦！"); button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, 0, screeny)); } else{ currentX = currentX-step; AbsoluteLayout.LayoutParams params = new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY); button.setLayoutParams(params); } } @SuppressWarnings("deprecation") private void moveRight(){ int temp = currentX+step; if(temp>=(screenx-buttonWidth)){ showToast("往右边到头了哦！"); button.setLayoutParams(new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, screenx-buttonWidth, currentY)); } else{ currentX = currentX+step; AbsoluteLayout.LayoutParams params = new AbsoluteLayout.LayoutParams(buttonWidth, buttonHeight, currentX, currentY); button.setLayoutParams(params); } } /** * 弹出提示信息 * @param text 提示信息 */ private void showToast(String text){ Toast.makeText(this, text, Toast.LENGTH_LONG).show(); } }

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       这里我们可以看到，要想监听这几个方向键，那么我们必须重写 public boolean onKeyDown(int keyCode, KeyEvent event)这个方法，该方法定义在Activity中，其中keyCode便是代表着你点击的那个键的标识符，KeyEvent 则是一个事件。

      需要注意的是，坐标问题：我们控制的按钮的坐标实际上是左上角的坐标。而屏幕的向左是X轴，向下是Y轴，也就是说，只要在屏幕内显示的组件，其坐标都是正数的。

     当然键盘中所有的键都可以监听的，我们亦可以来监听A-Z这些键，他们的keyCode依次是KEYCODE_A -------KEYCODE_Z.

     这里有一个小技巧，可以判断出用户输入的是什么A-Z那个字符，代码如下：

int code = 'A'+keycode-29;
char ch = (char)code;

int code = 'A'+keycode-29; char ch = (char)code;

如果我们无法获取当前的按键，我们可以通过keycode_unknown来捕捉。

控制音量大小：keycode_volume_down / keycode_volume_up.

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关于KeyEvent，它代表了我们点击键盘时的事件，看下图，我们可以创建自己的键盘事件

其中参数中的action，代表了用户的操作，值为ACTION_DOWN、ACTION_UP、ACTION_MULTIPLE其中的一个。而code则代表了我们的标识符，入上面提到的keycode_volume_down 就是一个code。