Android中属性资源的创建与使用

来源：互联网发布：j to e开发java模式编辑：程序博客网时间：2024/05/29 19:19

1.自定义一个属性资源res/values/attr.xml

<?xml version="1.0" encoding="utf-8"?><resources>    <attr name = "duration"  ></attr>    <declare-styleable name="AlphaImageView">        <attr name = "duration"  ></attr>    </declare-styleable></resources>

2.自定义包名/AlphaImageView.java

import java.util.Timer;import java.util.TimerTask;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.os.Handler;import android.os.Message;import android.util.AttributeSet;import android.widget.ImageView;/**  *图片从无到有渐变显示的imageview  *  */public class AlphaImageView extends ImageView{    //图片每次改变的透明度的大小    private int alphaDelta =0;    //图片当前的透明度    private int curAlpha = 0;    private final int SPEED = 150;    private Handler handler = new Handler(){        public void handleMessage(android.os.Message msg) {            if (msg.what == 0x123) {                curAlpha +=alphaDelta;//每次增加alphaDelta                if (curAlpha > 255) {                    curAlpha = 255;                }                AlphaImageView.this.setAlpha(curAlpha);//改变透明度            }        };    };    public AlphaImageView(Context context, AttributeSet attrs) {        super(context, attrs);        TypedArray typedArray = context.obtainStyledAttributes(attrs,R.styleable.AlphaImageView);        int duration = typedArray.getInt(R.styleable.AlphaImageView_duration, 0);        alphaDelta = 255*SPEED /duration;    }    @Override    protected void onDraw(Canvas canvas) {        this.setAlpha(curAlpha);        super.onDraw(canvas);        final Timer timer = new Timer();        timer.schedule(new TimerTask() {            @Override            public void run() {                Message msgMessage = new Message();                msgMessage.what = 0x123;                if (curAlpha>=255) {                    timer.cancel();                }else {                    handler.sendMessage(msgMessage);                }            }        }, 0, SPEED);    }}

3.布局文件中使用自定义属性

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    **xmlns:user="http://schemas.android.com/apk/res/项目包名"**    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"     android:gravity="center_horizontal">    <包名.AlphaImageView         android:layout_width="120dp"        android:layout_height="200dp"        android:src="@drawable/mid_pager_2"        **user:duration="6000"**        /></LinearLayout>

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