Android学习--keyboardEvent

键盘事件

    打开android-sdk/docs/reference/index.html

    在侧边栏找到android.app，点击它

   

    在右侧Classes找到Activity，点击

   

    进入Activity类之后你会找到它有一个方法onKeyDown，这就是键盘（手机键盘）事件处理的方法。

 

 

      创建工程TestKeyboardEvent，工程目录如下

 

activity_test_keyboard_event.xml 代码如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/screen"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical" >    <TextView        android:id="@+id/alphValue"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="center" />        <ImageViewandroid:id = "@+id/image"        android:src="@drawable/ic_launcher"        android:layout_gravity="center"        android:layout_width="wrap_content"        android:layout_height="wrap_content" />     </LinearLayout>

 android:src="@drawable/ic_launcher"这个drawable的值的问题，在R.java中存在资源ic_launcher，同时在drawable...文件夹中可以找到图片ic_launcher.png

 

TestKeyboardEvent.java 代码如下：

package com.hb.yooge.testkeyboardevent;import android.os.Bundle;import android.app.Activity;import android.util.Log;import android.view.KeyEvent;import android.view.Menu;import android.widget.ImageView;import android.widget.TextView;public class TestKeyboardEvent extends Activity {private static final String TAG = "TestKeyBoardEvent";private ImageView mImage;private TextView mAlphValueText;private int mAlphValue;private void findViewsById(){mImage = (ImageView) findViewById(R.id.image);mAlphValueText = (TextView) findViewById(R.id.alphValue);}    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_test_keyboard_event);        findViewsById();        mAlphValue = 100;        mImage.setAlpha(mAlphValue);        mAlphValueText.setText("Alpha = "+mAlphValue*100/0xff+"%");    }        @Override    public boolean onKeyDown(int keyCode, KeyEvent event)  {    Log.v(TAG, "onKeyDown: keyCode = " + keyCode);    Log.v(TAG, "onKeyDown: string = " + event.toString());        switch(keyCode){    case KeyEvent.KEYCODE_DPAD_UP:    ;    case KeyEvent.KEYCODE_DPAD_LEFT:    mAlphValue += 20;    break;    case KeyEvent.KEYCODE_DPAD_DOWN:    ;    case KeyEvent.KEYCODE_DPAD_RIGHT:    mAlphValue -= 20;    break;    default:    System.out.println("============================================");    }        if(mAlphValue >= 0xff){    mAlphValue = 0xff;    }    if(mAlphValue <= 0){    mAlphValue = 0;    }    mImage.setAlpha(mAlphValue);    mAlphValueText.setText("Alpha = " + mAlphValue + "%");            return super.onKeyDown(keyCode, event);    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        getMenuInflater().inflate(R.menu.activity_test_keyboard_event, menu);        return true;    }}

 

R.java 代码如下：

/* AUTO-GENERATED FILE.  DO NOT MODIFY. * * This class was automatically generated by the * aapt tool from the resource data it found.  It * should not be modified by hand. */package com.hb.yooge.testkeyboardevent;public final class R {    public static final class attr {    }    public static final class drawable {        public static final int ic_action_search=0x7f020000;        public static final int ic_launcher=0x7f020001;    }    public static final class id {        public static final int alphValue=0x7f070001;        public static final int image=0x7f070002;        public static final int menu_settings=0x7f070003;        public static final int screen=0x7f070000;    }    public static final class layout {        public static final int activity_test_keyboard_event=0x7f030000;    }    public static final class menu {        public static final int activity_test_keyboard_event=0x7f060000;    }    public static final class string {        public static final int app_name=0x7f040000;        public static final int hello_world=0x7f040001;        public static final int menu_settings=0x7f040002;        public static final int title_activity_test_keyboard_event=0x7f040003;    }    public static final class style {        public static final int AppTheme=0x7f050000;    }}

 

运行结果：按下左右可以看到图片的Alpha值改变了，同时图片变蒙了