Android编程实现图片的浏览、缩放、拖动和自动居中效果
本文实例讲述了Android编程实现图片的浏览、缩放、拖动和自动居中效果的方法。分享给大家供大家参考，具体如下：
Touch.java
/**
*图片浏览、缩放、拖动、自动居中
*/
publicclassTouchextendsActivityimplementsOnTouchListener{
Matrixmatrix=newMatrix();
MatrixsavedMatrix=newMatrix();
DisplayMetricsdm;
ImageViewimgView;
Bitmapbitmap;
floatminScaleR;//最小缩放比例
staticfinalfloatMAX_SCALE=4f;//最大缩放比例
staticfinalintNONE=0;//初始状态
staticfinalintDRAG=1;//拖动
staticfinalintZOOM=2;//缩放
intmode=NONE;
PointFprev=newPointF();
PointFmid=newPointF();
floatdist=1f;
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.scale);
imgView=(ImageView)findViewById(R.id.imag);//获取控件
bitmap=BitmapFactory.decodeResource(getResources(),this.getIntent()
.getExtras().getInt("IMG"));//获取图片资源
imgView.setImageBitmap(bitmap);//填充控件
imgView.setOnTouchListener(this);//设置触屏监听
dm=newDisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);//获取分辨率
minZoom();
center();
imgView.setImageMatrix(matrix);
}
/**
*触屏监听
*/
publicbooleanonTouch(Viewv,MotionEventevent){
switch(event.getAction()&MotionEvent.ACTION_MASK){
//主点按下
caseMotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
prev.set(event.getX(),event.getY());
mode=DRAG;
break;
//副点按下
caseMotionEvent.ACTION_POINTER_DOWN:
dist=spacing(event);
//如果连续两点距离大于10，则判定为多点模式
if(spacing(event)>10f){
savedMatrix.set(matrix);
midPoint(mid,event);
mode=ZOOM;
}
break;
caseMotionEvent.ACTION_UP:
caseMotionEvent.ACTION_POINTER_UP:
mode=NONE;
break;
caseMotionEvent.ACTION_MOVE:
if(mode==DRAG){
matrix.set(savedMatrix);
matrix.postTranslate(event.getX()-prev.x,event.getY()
-prev.y);
}elseif(mode==ZOOM){
floatnewDist=spacing(event);
if(newDist>10f){
matrix.set(savedMatrix);
floattScale=newDist/dist;
matrix.postScale(tScale,tScale,mid.x,mid.y);
}
}
break;
}
imgView.setImageMatrix(matrix);
CheckView();
returntrue;
}
/**
*限制最大最小缩放比例，自动居中
*/
privatevoidCheckView(){
floatp[]=newfloat[9];
matrix.getValues(p);
if(mode==ZOOM){
if(p[0]<minScaleR){
matrix.setScale(minScaleR,minScaleR);
}
if(p[0]>MAX_SCALE){
matrix.set(savedMatrix);
}
}
center();
}
/**
*最小缩放比例，最大为100%
*/
privatevoidminZoom(){
minScaleR=Math.min(
(float)dm.widthPixels/(float)bitmap.getWidth(),
(float)dm.heightPixels/(float)bitmap.getHeight());
if(minScaleR<1.0){
matrix.postScale(minScaleR,minScaleR);
}
}
privatevoidcenter(){
center(true,true);
}
/**
*横向、纵向居中
*/
protectedvoidcenter(booleanhorizontal,booleanvertical){
Matrixm=newMatrix();
m.set(matrix);
RectFrect=newRectF(0,0,bitmap.getWidth(),bitmap.getHeight());
m.mapRect(rect);
floatheight=rect.height();
floatwidth=rect.width();
floatdeltaX=0,deltaY=0;
if(vertical){
//图片小于屏幕大小，则居中显示。大于屏幕，上方留空则往上移，下方留空则往下移
intscreenHeight=dm.heightPixels;
if(height<screenHeight){
deltaY=(screenHeight-height)/2-rect.top;
}elseif(rect.top>0){
deltaY=-rect.top;
}elseif(rect.bottom<screenHeight){
deltaY=imgView.getHeight()-rect.bottom;
}
}
if(horizontal){
intscreenWidth=dm.widthPixels;
if(width<screenWidth){
deltaX=(screenWidth-width)/2-rect.left;
}elseif(rect.left>0){
deltaX=-rect.left;
}elseif(rect.right<screenWidth){
deltaX=screenWidth-rect.right;
}
}
matrix.postTranslate(deltaX,deltaY);
}
/**
*两点的距离
*/
privatefloatspacing(MotionEventevent){
floatx=event.getX(0)-event.getX(1);
floaty=event.getY(0)-event.getY(1);
returnFloatMath.sqrt(x*x+y*y);
}
/**
*两点的中点
*/
privatevoidmidPoint(PointFpoint,MotionEventevent){
floatx=event.getX(0)+event.getX(1);
floaty=event.getY(0)+event.getY(1);
point.set(x/2,y/2);
}
}
scale.xml
<?xmlversion="1.0"encoding="utf-8"?> <FrameLayoutxmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_gravity="center"> <ImageView android:id="@+id/imag" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_gravity="center" android:scaleType="matrix"> </ImageView> </FrameLayout>
希望本文所述对大家Android程序设计有所帮助。