第九章 Android-UI组件(2)

一、图像视图（ImageView）

布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:stretchColumns="*"
    android:layout_gravity="center"
    android:id="@+id/Tablelayout01">
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center">
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/bt1"
            android:text="text1"/>
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/bt2"
            android:text="text1"/>
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/bt3"
            android:text="text1"/></LinearLayout>
    <ImageView
        android:id="@+id/iv"
        android:scaleType="center"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/plane"/>
</LinearLayout>

逻辑

package com.example.administrator.app1;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {
    private Button btn1,btn2,btn3;
    private int alpha=255;
    private int curr=0;
    private int[] colors={R.drawable.bg_grey,R.drawable.bg_login,R.drawable.frame,R.drawable.logo};
    private ImageView iv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn1=(Button)findViewById(R.id.bt1);
        btn2=(Button)findViewById(R.id.bt2);
        btn3=(Button)findViewById(R.id.bt3);
        btn1.setOnClickListener(new MyListener());
        btn2.setOnClickListener(new MyListener());
        iv=(ImageView)findViewById(R.id.iv);
        btn3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                iv.setImageResource(colors[curr++%colors.length]);
            }
        });

    }
    class MyListener implements   View.OnClickListener{
        @Override
        public void onClick(View v) {
            if(v.equals(btn1)) {
                Log.i("tag","11111");
                alpha-=20;
                if(alpha>=255){
                    alpha=255;
                }
                Log.i("tag","11111222222");
            } else if(v==btn2) {
                Log.i("tag","2222");
                alpha-=20;
                if(alpha<=0)
                {
                    alpha=0;
                }
                Log.i("tag","22222333333");
            }
            Log.d("tag", alpha+"");
            iv.setImageAlpha(alpha);
        }

    }
    }