这是您可以使用的一种方法（但是，有很多实现相同方法的可能性）。它基于创建用于绘制和跟踪选择矩形的自定义视图。此外，您可以onTouch()在您的自定义视图中应用逻辑OnTouchListener()。
主要布局：
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:id="@+id/root"
android:background="@android:color/background_dark">
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/image"
android:src="@drawable/up_image"
android:scaleType="fitXY" />
<com.example.TestApp.DragRectView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/dragRect" />
</RelativeLayout>
自定义视图：
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
public class DragRectView extends View {
private Paint mRectPaint;
private int mStartX = 0;
private int mStartY = 0;
private int mEndX = 0;
private int mEndY = 0;
private boolean mDrawRect = false;
private TextPaint mTextPaint = null;
private OnUpCallback mCallback = null;
public interface OnUpCallback {
void onRectFinished(Rect rect);
}
public DragRectView(final Context context) {
super(context);
init();
}
public DragRectView(final Context context, final AttributeSet attrs) {
super(context, attrs);
init();
}
public DragRectView(final Context context, final AttributeSet attrs, final int defStyle) {
super(context, attrs, defStyle);
init();
}
/**
* Sets callback for up
*
* @param callback {@link OnUpCallback}
*/
public void setOnUpCallback(OnUpCallback callback) {
mCallback = callback;
}
/**
* Inits internal data
*/
private void init() {
mRectPaint = new Paint();
mRectPaint.setColor(getContext().getResources().getColor(android.R.color.holo_green_light));
mRectPaint.setStyle(Paint.Style.STROKE);
mRectPaint.setStrokeWidth(5); // TODO: should take from resources
mTextPaint = new TextPaint();
mTextPaint.setColor(getContext().getResources().getColor(android.R.color.holo_green_light));
mTextPaint.setTextSize(20);
}
@Override
public boolean onTouchEvent(final MotionEvent event) {
// TODO: be aware of multi-touches
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mDrawRect = false;
mStartX = (int) event.getX();
mStartY = (int) event.getY();
invalidate();
break;
case MotionEvent.ACTION_MOVE:
final int x = (int) event.getX();
final int y = (int) event.getY();
if (!mDrawRect || Math.abs(x - mEndX) > 5 || Math.abs(y - mEndY) > 5) {
mEndX = x;
mEndY = y;
invalidate();
}
mDrawRect = true;
break;
case MotionEvent.ACTION_UP:
if (mCallback != null) {
mCallback.onRectFinished(new Rect(Math.min(mStartX, mEndX), Math.min(mStartY, mEndY),
Math.max(mEndX, mStartX), Math.max(mStartY, mEndY)));
}
invalidate();
break;
default:
break;
}
return true;
}
@Override
protected void onDraw(final Canvas canvas) {
super.onDraw(canvas);
if (mDrawRect) {
canvas.drawRect(Math.min(mStartX, mEndX), Math.min(mStartY, mEndY),
Math.max(mEndX, mStartX), Math.max(mEndY, mStartY), mRectPaint);
canvas.drawText(" (" + Math.abs(mStartX - mEndX) + ", " + Math.abs(mStartY - mEndY) + ")",
Math.max(mEndX, mStartX), Math.max(mEndY, mStartY), mTextPaint);
}
}
}
活动很简单：
public class MyActivity extends Activity {
private static final String TAG = "MyActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final DragRectView view = (DragRectView) findViewById(R.id.dragRect);
if (null != view) {
view.setOnUpCallback(new DragRectView.OnUpCallback() {
@Override
public void onRectFinished(final Rect rect) {
Toast.makeText(getApplicationContext(), "Rect is (" + rect.left + ", " + rect.top + ", " + rect.right + ", " + rect.bottom + ")",
Toast.LENGTH_LONG).show();
}
});
}
}
}
输出如下：
