Android 图片的浏览、缩放、拖动和自动居中

来源：互联网发布：linux运行java jar包编辑：程序博客网时间：2024/05/03 06:00

这篇文章的代码直接copy就可以用。

家可以先去了解下Android Matrix基础+详解。

Activity文件

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);    }}

布局文件

scale.xml

<?xml version="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>

转自《Android 图片的浏览、缩放、拖动和自动居中》

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