The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
/*
* Copyright (C) 2010 The Android开源工程
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.apis.view;
import com.example.android.apis.R;
import android.content.ClipData;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.*;
import android.os.SystemClock;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.DragEvent;
import android.view.View;
import android.widget.TextView;
public class DraggableDot extends View {
static final String TAG = "DraggableDot";
private boolean mDragInProgress;
private boolean mHovering;
private boolean mAcceptsDrag;
TextView mReportView;
private Paint mPaint;
private TextPaint mLegendPaint;
private Paint mGlow;
private static final int NUM_GLOW_STEPS = 10;
private static final int GREEN_STEP = 0x0000FF00 / NUM_GLOW_STEPS;
private static final int WHITE_STEP = 0x00FFFFFF / NUM_GLOW_STEPS;
private static final int ALPHA_STEP = 0xFF000000 / NUM_GLOW_STEPS;
int mRadius;
int mAnrType;
CharSequence mLegend;
static final int ANR_NONE = 0;
static final int ANR_SHADOW = 1;
static final int ANR_DROP = 2;
void sleepSixSeconds() {
// hang forever; good for producing ANRs
long start = SystemClock.uptimeMillis();
do {
try { Thread.sleep(1000); } catch (InterruptedException e) {}
} while (SystemClock.uptimeMillis() < start + 6000);
}
// Shadow builder that can ANR if desired
class ANRShadowBuilder extends DragShadowBuilder {
boolean mDoAnr;
public ANRShadowBuilder(View view, boolean doAnr) {
super(view);
mDoAnr = doAnr;
}
@Override
public void onDrawShadow(Canvas canvas) {
if (mDoAnr) {
sleepSixSeconds();
}
super.onDrawShadow(canvas);
}
}
public DraggableDot(Context context, AttributeSet attrs) {
super(context, attrs);
setFocusable(true);
setClickable(true);
mLegend = "";
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setStrokeWidth(6);
mPaint.setColor(0xFFD00000);
mLegendPaint = new TextPaint();
mLegendPaint.setAntiAlias(true);
mLegendPaint.setTextAlign(Paint.Align.CENTER);
mLegendPaint.setColor(0xFFF0F0FF);
mGlow = new Paint();
mGlow.setAntiAlias(true);
mGlow.setStrokeWidth(1);
mGlow.setStyle(Paint.Style.STROKE);
// look up any layout-defined attributes
TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.DraggableDot);
final int N = a.getIndexCount();
for (int i = 0; i < N; i++) {
int attr = a.getIndex(i);
switch (attr) {
case R.styleable.DraggableDot_radius: {
mRadius = a.getDimensionPixelSize(attr, 0);
} break;
case R.styleable.DraggableDot_legend: {
mLegend = a.getText(attr);
} break;
case R.styleable.DraggableDot_anr: {
mAnrType = a.getInt(attr, 0);
} break;
}
}
Log.i(TAG, "DraggableDot @ " + this + " : radius=" + mRadius + " legend='" + mLegend
+ "' anr=" + mAnrType);
setOnLongClickListener(new View.OnLongClickListener() {
public boolean onLongClick(View v) {
ClipData data = ClipData.newPlainText("dot", "Dot : " + v.toString());
v.startDrag(data, new ANRShadowBuilder(v, mAnrType == ANR_SHADOW),
(Object)v, 0);
return true;
}
});
}
void setReportView(TextView view) {
mReportView = view;
}
@Override
protected void onDraw(Canvas canvas) {
float wf = getWidth();
float hf = getHeight();
final float cx = wf/2;
final float cy = hf/2;
wf -= getPaddingLeft() + getPaddingRight();
hf -= getPaddingTop() + getPaddingBottom();
float rad = (wf < hf) ? wf/2 : hf/2;
canvas.drawCircle(cx, cy, rad, mPaint);
if (mLegend != null && mLegend.length() > 0) {
canvas.drawText(mLegend, 0, mLegend.length(),
cx, cy + mLegendPaint.getFontSpacing()/2,
mLegendPaint);
}
// if we're in the middle of a drag, light up as a potential target
if (mDragInProgress && mAcceptsDrag) {
for (int i = NUM_GLOW_STEPS; i > 0; i--) {
int color = (mHovering) ? WHITE_STEP : GREEN_STEP;
color = i*(color | ALPHA_STEP);
mGlow.setColor(color);
canvas.drawCircle(cx, cy, rad, mGlow);
rad -= 0.5f;
canvas.drawCircle(cx, cy, rad, mGlow);
rad -= 0.5f;
}
}
}
@Override
protected void onMeasure(int widthSpec, int heightSpec) {
int totalDiameter = 2*mRadius + getPaddingLeft() + getPaddingRight();
setMeasuredDimension(totalDiameter, totalDiameter);
}
/**
* Drag and drop
*/
@Override
public boolean onDragEvent(DragEvent event) {
boolean result = false;
switch (event.getAction()) {
case DragEvent.ACTION_DRAG_STARTED: {
// claim to accept any dragged content
Log.i(TAG, "Drag started, event=" + event);
// cache whether we accept the drag to return for LOCATION events
mDragInProgress = true;
mAcceptsDrag = result = true;
// Redraw in the new visual state if we are a potential drop target
if (mAcceptsDrag) {
invalidate();
}
} break;
case DragEvent.ACTION_DRAG_ENDED: {
Log.i(TAG, "Drag ended.");
if (mAcceptsDrag) {
invalidate();
}
mDragInProgress = false;
mHovering = false;
} break;
case DragEvent.ACTION_DRAG_LOCATION: {
// we returned true to DRAG_STARTED, so return true here
Log.i(TAG, "... seeing drag locations ...");
result = mAcceptsDrag;
} break;
case DragEvent.ACTION_DROP: {
Log.i(TAG, "Got a drop! dot=" + this + " event=" + event);
if (mAnrType == ANR_DROP) {
sleepSixSeconds();
}
processDrop(event);
result = true;
} break;
case DragEvent.ACTION_DRAG_ENTERED: {
Log.i(TAG, "Entered dot @ " + this);
mHovering = true;
invalidate();
} break;
case DragEvent.ACTION_DRAG_EXITED: {
Log.i(TAG, "Exited dot @ " + this);
mHovering = false;
invalidate();
} break;
default:
Log.i(TAG, "other drag event: " + event);
result = mAcceptsDrag;
break;
}
return result;
}
private void processDrop(DragEvent event) {
final ClipData data = event.getClipData();
final int N = data.getItemCount();
for (int i = 0; i < N; i++) {
ClipData.Item item = data.getItemAt(i);
Log.i(TAG, "Dropped item " + i + " : " + item);
if (mReportView != null) {
String text = item.coerceToText(getContext()).toString();
if (event.getLocalState() == (Object) this) {
text += " : Dropped on self!";
}
mReportView.setText(text);
}
}
}
}