前几天做项目用到相机拍照，之后能对图片进行缩放，拖拽，在此我将其单独抽取出来，后面用到时直接拿来用就行了！
效果图：
注：这里不仅能按钮缩放，还能多点触摸缩放和拖拽功能！
1.布局：
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<?
xml
version
=
"1.0"
encoding
=
"UTF-8"
?>
<
FrameLayout
xmlns:android
=
"http://schemas.android.com/apk/res/android"
android:id
=
"@+id/flayout_img_display"
android:layout_width
=
"fill_parent"
android:layout_height
=
"fill_parent"
android:orientation
=
"vertical"
>
<
LinearLayout
android:id
=
"@+id/linearLayout_img_display"
android:layout_width
=
"fill_parent"
android:layout_height
=
"fill_parent"
android:layout_gravity
=
"center"
android:gravity
=
"center"
>
<
ImageView
android:id
=
"@+id/img_display"
android:layout_width
=
"fill_parent"
android:layout_height
=
"wrap_content"
android:paddingBottom
=
"5.0dip"
android:paddingTop
=
"5.0dip"
android:scaleType
=
"matrix"
/>
</
LinearLayout
>
<
RelativeLayout
android:id
=
"@+id/relativeLayout1"
android:layout_width
=
"fill_parent"
android:layout_height
=
"wrap_content"
>
<
Button
android:id
=
"@+id/btn_min"
android:layout_width
=
"wrap_content"
android:layout_height
=
"wrap_content"
android:layout_alignParentBottom
=
"true"
android:layout_alignParentLeft
=
"true"
android:enabled
=
"false"
android:text
=
"缩小"
/>
<
Button
android:id
=
"@+id/btn_out"
android:layout_width
=
"wrap_content"
android:layout_height
=
"wrap_content"
android:layout_alignParentBottom
=
"true"
android:layout_alignParentRight
=
"true"
android:text
=
"放大"
/>
</
RelativeLayout
>
</
FrameLayout
>
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2.就一个类：
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import
android.app.Activity;
import
android.content.Intent;
import
android.graphics.Bitmap;
import
android.graphics.BitmapFactory;
import
android.graphics.Matrix;
import
android.graphics.PointF;
import
android.os.Bundle;
import
android.util.FloatMath;
import
android.util.Log;
import
android.view.MotionEvent;
import
android.view.View;
import
android.view.View.OnClickListener;
import
android.view.View.OnTouchListener;
import
android.widget.Button;
import
android.widget.FrameLayout;
import
android.widget.ImageView;
import
android.widget.LinearLayout;
/**
* 缩放图片界面
* @author ZHF
*
*/
public
class
MainActivity
extends
Activity {
public
static
final
String TAG =
"ImgDisplayActivity"
;
//控件声明
private
Button btnZoomin, btnZoomout;
private
ImageView imgDisPlay;
private
LinearLayout lLayoutDisplay;
private
FrameLayout fLayoutDisplay;
private
Bitmap bitmap;
private
int
imgId =
0
;
private
double
scale_in =
0.8
;
//缩小比例
private
double
scale_out =
1.25
;
//放大比例
private
float
scaleWidth =
1
;
private
float
scaleHeight =
1
;
//模式：0：什么都不干；1：拖拽； 2：缩放
public
static
final
int
NONE =
0
;
public
static
final
int
DRAG =
1
;
public
static
final
int
ZOOM =
2
;
//声明触发的事件模式
private
int
mode = NONE;
private
Matrix matrix;
//矩阵
private
Matrix currMatrix;
//当前矩阵
private
PointF starPoint;
private
PointF midPoint;
private
float
startDistance;
@Override
protected
void
onCreate(Bundle savedInstanceState) {
super
.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//初始化
fLayoutDisplay = (FrameLayout) findViewById(R.id.flayout_img_display);
lLayoutDisplay = (LinearLayout) findViewById(R.id.linearLayout_img_display);
imgDisPlay = (ImageView) findViewById(R.id.img_display);
btnZoomin = (Button) findViewById(R.id.btn_min);
btnZoomout = (Button) findViewById(R.id.btn_out);
matrix =
new
Matrix();
//保存拖拽变化
currMatrix =
new
Matrix();
// 当前的
starPoint =
new
PointF();
//开始点的位置
btnZoomin.setOnClickListener(
new
OnClickListener() {
@Override
public
void
onClick(View v) {
zoomIn();
}
});
btnZoomout.setOnClickListener(
new
OnClickListener() {
@Override
public
void
onClick(View v) {
zoomOut();
//放大
}
});
imgDisPlay.setImageResource(R.drawable.img);
//给图片绑定监听器哦
imgDisPlay.setOnTouchListener(
new
ImageViewOnTouchListener());
}
/**放大操作**/
private
void
zoomOut() {
reSizeBmp(scale_out);
btnZoomin.setEnabled(
true
);
}
/**缩小操作**/
private
void
zoomIn() {
reSizeBmp(scale_in);
}
/**接收传入的缩放比例实现缩放**/
private
void
reSizeBmp(
double
scale) {
//缩放比例
scaleWidth = (
float
) (scaleWidth * scale);
scaleHeight = (
float
) (scaleHeight * scale);
Matrix matrix =
new
Matrix();
matrix.postScale(scaleWidth, scaleHeight);
//设计缩放比例
imgDisPlay.setImageMatrix(matrix);
}
/**计算触摸实现缩放**/
final
class
ImageViewOnTouchListener
implements
OnTouchListener{
@Override
public
boolean
onTouch(View v, MotionEvent event) {
switch
(event.getAction() & MotionEvent.ACTION_MASK) {
case
MotionEvent.ACTION_DOWN:
//一只手指按下
Log.i(TAG,
"一只手指按下"
);
currMatrix.set(matrix);
starPoint.set(event.getX(), event.getY());
mode = DRAG;
break
;
case
MotionEvent.ACTION_POINTER_DOWN:
//如果有一只手指按下屏幕，后续又有一个手指按下 // 两只手指按下
Log.i(TAG,
"又有一只手指按下"
);
startDistance = distance(event);
//记下两点的距离
Log.i(TAG, startDistance+
""
);
if
(startDistance > 5f) {
//两个手指之间的最小距离像素大于5，认为是多点触摸
mode = ZOOM;
currMatrix.set(matrix);
midPoint = getMidPoint(event);
//记下两个点之间的中心点
}
break
;
case
MotionEvent.ACTION_MOVE:
if
(mode == DRAG) {
//拖拽模式
Log.i(TAG,
"一只手指在拖拽"
);
//开始--》结束点的距离
float
dx = event.getX() - starPoint.x;
float
dy = event.getY() - starPoint.y;
matrix.set(currMatrix);
matrix.postTranslate(dx, dy);
//移动到指定点：矩阵移动比例；eg:缩放有缩放比例
}
else
if
(mode == ZOOM) {
//缩放模式
Log.i(TAG,
"正在缩放"
);
float
distance = distance(event);
//两点之间的距离
if
(distance > 5f) {
matrix.set(currMatrix);
float
cale = distance / startDistance;
matrix.preScale(cale, cale, midPoint.x, midPoint.y);
//进行比例缩放
}
}
break
;
case
MotionEvent.ACTION_UP:
//最后一只手指离开屏幕后触发此事件
case
MotionEvent.ACTION_POINTER_UP:
//一只手指离开屏幕，但还有一只手指在上面会触此事件
//什么都没做
mode = NONE;
break
;
default
:
break
;
}
imgDisPlay.setImageMatrix(matrix);
//两只手指的缩放
return
true
;
}
}
/**计算两点之间的距离像素**/
private
float
distance(MotionEvent e) {
float
eX = e.getX(
1
) - e.getX(
0
);
//后面的点坐标 - 前面点的坐标
float
eY = e.getY(
1
) - e.getY(
0
);
return
FloatMath.sqrt(eX * eX + eY * eY);
}
/**计算两点之间的中心点**/
private
PointF getMidPoint(MotionEvent event) {
float
x = (event.getX(
1
) - event.getX(
0
)) /
2
;
float
y = (event.getY(
1
) - event.getY(
0
)) /
2
;
return
new
PointF(x,y);
}
}
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ok！主要的算法就在ImageViewOnTouchListener监听器当中，要考虑那三种情况（缩放、拖拽、什么都不干），另外需要注意的就是，单个手指和两个以上手指的情况。
源码下载:http://down.51cto.com/data/876165
本文转自zhf651555765 51CTO博客，原文链接：http://blog.51cto.com/smallwoniu/1252191，如需转载请自行联系原作者
