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 */ public class Touch extends Activity implements OnTouchListener { Matrix matrix = new Matrix(); Matrix savedMatrix = new Matrix(); DisplayMetrics dm; ImageView imgView; Bitmap bitmap; float minScaleR;// 最小缩放比例 static final float MAX_SCALE = 4f;// 最大缩放比例 static final int NONE = 0;// 初始状态 static final int DRAG = 1;// 拖动 static final int ZOOM = 2;// 缩放 int mode = NONE; PointF prev = new PointF(); PointF mid = new PointF(); float dist = 1f; @Override public void onCreate(Bundle savedInstanceState) { 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 = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(dm);// 获取分辨率 minZoom(); center(); imgView.setImageMatrix(matrix); } /** * 触屏监听 */ public boolean onTouch(View v, MotionEvent event) { switch (event.getAction() & MotionEvent.ACTION_MASK) { // 主点按下 case MotionEvent.ACTION_DOWN: savedMatrix.set(matrix); prev.set(event.getX(), event.getY()); mode = DRAG; break; // 副点按下 case MotionEvent.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; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_POINTER_UP: mode = NONE; break; case MotionEvent.ACTION_MOVE: if (mode == DRAG) { matrix.set(savedMatrix); matrix.postTranslate(event.getX() - prev.x, event.getY() - prev.y); } else if (mode == ZOOM) { float newDist = spacing(event); if (newDist > 10f) { matrix.set(savedMatrix); float tScale = newDist / dist; matrix.postScale(tScale, tScale, mid.x, mid.y); } } break; } imgView.setImageMatrix(matrix); CheckView(); return true; } /** * 限制最大最小缩放比例，自动居中 */ private void CheckView() { float p[] = new float[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% */ private void minZoom() { minScaleR = Math.min( (float) dm.widthPixels / (float) bitmap.getWidth(), (float) dm.heightPixels / (float) bitmap.getHeight()); if (minScaleR < 1.0) { matrix.postScale(minScaleR, minScaleR); } } private void center() { center(true, true); } /** * 横向、纵向居中 */ protected void center(boolean horizontal, boolean vertical) { Matrix m = new Matrix(); m.set(matrix); RectF rect = new RectF(0, 0, bitmap.getWidth(), bitmap.getHeight()); m.mapRect(rect); float height = rect.height(); float width = rect.width(); float deltaX = 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 int screenHeight = dm.heightPixels; if (height < screenHeight) { deltaY = (screenHeight - height) / 2 - rect.top; } else if (rect.top > 0) { deltaY = -rect.top; } else if (rect.bottom < screenHeight) { deltaY = imgView.getHeight() - rect.bottom; } } if (horizontal) { int screenWidth = dm.widthPixels; if (width < screenWidth) { deltaX = (screenWidth - width) / 2 - rect.left; } else if (rect.left > 0) { deltaX = -rect.left; } else if (rect.right < screenWidth) { deltaX = screenWidth - rect.right; } } matrix.postTranslate(deltaX, deltaY); } /** * 两点的距离 */ private float spacing(MotionEvent event) { float x = event.getX(0) - event.getX(1); float y = event.getY(0) - event.getY(1); return FloatMath.sqrt(x * x + y * y); } /** * 两点的中点 */ private void midPoint(PointF point, MotionEvent event) { float x = event.getX(0) + event.getX(1); float y = event.getY(0) + event.getY(1); point.set(x / 2, y / 2); } }
scale.xml
<"1.0" encoding="utf-8"?> <FrameLayout xmlns: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。
【Android编程实现图片的浏览、缩放、拖动和自动居中效果】相关文章：