Android界面编程之四 第三组UI组件：ImageView及其子类

ImageView继承自View组件，ImageView还派生了ImageButton、ZoomButton等组件

Image支持的XML属性如下：

android:adjustViewBounds		是否调整自己的边界来保持所显示图片的长宽比
android:cropToPadding		若属性设为true，该组件将会被裁剪到保留该ImageView的padding
android:maxHeight		设置ImageView的最大高度
android:maxWidth
android:scaleType		设置所显示的图片如何缩放或移动以适应ImageView的大小
android:src		设置ImageView所显示的Drawable对象的ID

android:scaleType属性可指定如下属性值：

matrix

fitXY

fitStart

fitCenter

fitEnd

center

centerCrop

centerInside

为控制ImageView显示的图片，ImageView提供了如下方法：

setImageBitmap(Bitmap bm)

setImageDrawable(Drawable drawable)

setImageResource(int resId)

setImageURI(Uri uri)

oops 陷阱：

R.drawable.xxxxx(此处xxx不可为1，2，3，4等数字，否则会导致Build失败)

图片显示示例程序代码：

public class MainActivity extends ActionBarActivity {

int [] images = new int []{
R.drawable. pic1 ,
R.drawable. pic2 ,
R.drawable. pic3 ,
R.drawable. pic4 ,
R.drawable. pic5
};
int currentImg = 2;
private int alpha = 255;
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super .onCreate(savedInstanceState);
        setContentView(R.layout. activity_main );
        final Button plus = (Button) findViewById(R.id. plus );

       
        final Button minus = (Button) findViewById(R.id. minus );
        final ImageView image1 = (ImageView) findViewById(R.id. image1 );
        final ImageView image2 = (ImageView) findViewById(R.id. image2 );
        final Button next = (Button) findViewById(R.id. next );
        final Button last = (Button) findViewById(R.id. last );
        next.setOnClickListener( new OnClickListener()
        {
        @Override
        public void onClick(View v)
        {
        image1.setImageResource(
        images [++ currentImg % images . length ]);
        }
        });
        last.setOnClickListener( new OnClickListener()
        {
        @Override
        public void onClick(View v)
        {
        if ( currentImg == 0)
        {
        currentImg = images . length ;
        }
        image1.setImageResource(
        images [-- currentImg ]);
        }
        });
        //change alpha

       
        OnClickListener listener = new OnClickListener()
        {
        @Override
        public void onClick(View v)
        {
        if (v == plus)
        {
        alpha += 20;
        }
        if (v == minus)
        {
        alpha -= 20;
        }
        if ( alpha >= 255)
        {
        alpha = 255;
        }
        if ( alpha <= 0)
        {
        alpha = 0;
        }
        image1.setAlpha( alpha );
        }
        };
        plus.setOnClickListener(listener);
        minus.setOnClickListener(listener);
       
        image1.setOnTouchListener( new OnTouchListener()
        {
        @Override
        public boolean onTouch(View view, MotionEvent event)
        {
        BitmapDrawable bitmapDrawable = (BitmapDrawable) image1.getDrawable();
        Bitmap bitmap = bitmapDrawable.getBitmap();
        double scale = bitmap.getWidth()/320.0;
        int x = ( int ) (event.getX()*scale);
        int y = ( int ) (event.getY()*scale);
        if (x + 120 > bitmap.getWidth())
        {
        x = bitmap.getWidth() - 120;
        }
        if (y + 120 > bitmap.getHeight())
        {
        y = bitmap.getHeight() - 120;
        }
        image2.setImageBitmap(Bitmap.createBitmap(bitmap,x,y,120,120));
        image2.setAlpha( alpha );
        return false ;
        }

        });

    }

}

ImageView 派生了如下两个子类：

ImageButton：imageButton上显示图片

QuickContactBadge

ImageButton派生了一个ZoomButton，为ZoomButton的android:src属性分别指定btn_minus、btn_plus，即可实现“放大”、“缩小”按钮

QuickContactBadge继承了ImageView，它的本质也是图片，android:src属性可设为显示图片，该图片可以关联到联系人，

assignContactFromEmail(String emailAddress, boolean lazyLookup)

assignContactFromPhone(String phoneNumber, boolean lazyLookup)

assignContactUri(Uri contactUri)

关联联系人程序代码如下：

xml文件

< LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
    xmlns:tools = "http://schemas.android.com/tools"
    android:layout_width = "match_parent"
    android:layout_height = "match_parent"

     >

    < QuickContactBadge
        android:id = "@+id/badge"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:src = "@drawable/ic_launcher"
        />
    < TextView
        android:layout_width = "match_parent"
        android:layout_height = "wrap_content"
        android:text = "My icon"
        android:textSize = "16dp"
        />

</ LinearLayout >

Java程序：

public class MainActivity extends ActionBarActivity {

QuickContactBadge badge ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super .onCreate(savedInstanceState);
        setContentView(R.layout. activity_main );
        badge = (QuickContactBadge) findViewById(R.id. badge );
        badge .assignContactFromPhone( "15926563025" , false );
    }