我尝试从文件资源中绘制ImageView。这是我的代码：
private Bitmap myBitmap;
private Bitmap mutableBitmap;
private Canvas canvas;
private Paint paint;
private ImageView img;
@Override
protected void onCreate (Bundle savedInstanceState) {
super.onCreate (savedInstanceState);
setContentView (R.layout.layout_imagefullscreen);
paint = new Paint();
paint.setStrokeWidth(11);
paint.setColor(Color.YELLOW);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeCap(Paint.Cap.ROUND);
View decorView = getWindow().getDecorView();
int uiOptions = View.SYSTEM_UI_FLAG_LOW_PROFILE;
decorView.setSystemUiVisibility(uiOptions);
...
if (imageFileFullPathName != null) {
try {
File imgFile = new File (imageFileFullPathName);
if (imgFile.exists ()) {
myBitmap = BitmapFactory.decodeFile(imgFile.getAbsolutePath());
mutableBitmap = myBitmap.copy(Bitmap.Config.ARGB_8888, true);
canvas = new Canvas(mutableBitmap);
img.setImageBitmap(mutableBitmap);
Matrix m = img.getImageMatrix();
canvas.setMatrix(m);
}
} catch (Exception e) {
e.printStackTrace ();
}
}
img.setOnTouchListener (new OnTouchListener() {
float startX, startY;
float stopX, stopY;
@Override
public boolean onTouch (View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
startX = event.getX();
startY = event.getY();
Log.i("---> DOWN X", String.valueOf(startX));
Log.i("---> DOWN Y", String.valueOf(startY));
break;
case MotionEvent.ACTION_MOVE:
stopX = event.getRawX();
stopY = event.getRawY();
Log.i("---> MOVE X", String.valueOf(stopX));
Log.i("---> MOVE Y", String.valueOf(stopY));
canvas.drawLine(startX, startY, stopX, stopY, paint);
img.invalidate();
startX = event.getRawX();
startY = event.getRawY();
img.setImageBitmap(mutableBitmap);
break;
case MotionEvent.ACTION_UP:
stopX = event.getRawX();
stopY = event.getRawY();
Log.i("---> UP X", String.valueOf(stopX));
Log.i("---> UP Y", String.valueOf(stopY));
canvas.drawLine(startX, startY, stopX, stopY, paint);
img.invalidate();
break;
default:
break;
}
v.performClick();
return true;
}
});
}
}'
但是当我在ImageView上移动手指时，线条不会跟随我的手指，而是只限制在屏幕的左上角。我也尝试将getRawX()更改为getX()，但此问题仍然存在。我相信问题与坐标变换有关，但无法弄清楚如何解决它。请帮忙，谢谢！
布局 xml 文件：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:background="@color/Black">
<ImageView
android:id="@+id/imagefullscreenview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:src="@drawable/ic_launcher"/>
</LinearLayout>
从您的代码来看，您似乎正在尝试按照触摸的手指进行绘制。所以这是你画画的方式...
public class MainActivity extends Activity implements SurfaceHolder.Callback, OnClickListener, OnTouchListener {
SurfaceView sv;
SurfaceHolder sh;
RenderingThread thread;
Canvas canvas = null;
int Width = 0, Height = 0;
Button btnClear;
Path path = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
try{
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
setContentView(R.layout.activity_main);
sv = (SurfaceView)findViewById(R.id.sv);
sv.setOnTouchListener(this);
btnClear = (Button)findViewById(R.id.btnClear);
path = new Path();
sh = sv.getHolder();
if(sh != null)
{
sh.addCallback(this);
}
else
{
Toast.makeText(getApplicationContext(), "Failed to initialize", Toast.LENGTH_SHORT).show();
finish();
}
}catch(Throwable ex)
{
ex.printStackTrace();
Toast.makeText(getApplicationContext(), "Failed to start", Toast.LENGTH_SHORT).show();
finish();
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
try{
Width = width;
Height = height;
thread = new RenderingThread(holder, width, height);
canvas = new Canvas(thread.drawingBitmap);
thread.start();
}catch(Throwable ex) {
ex.printStackTrace();
Toast.makeText(getApplicationContext(), "Failed to initialize", Toast.LENGTH_SHORT).show();
finish();
}
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
sv.setWillNotDraw(false);
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
thread.RequestStop();
}
public boolean onTouch(View v, MotionEvent event) {
switch(event.getAction())
{
case MotionEvent.ACTION_DOWN:
path.moveTo(event.getRawX(), event.getRawY());
break;
case MotionEvent.ACTION_MOVE:
Paint paint = new Paint();
paint.setColor(Color.RED);
paint.setAntiAlias(true);
paint.setColor(Color.BLUE);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(5);
CornerPathEffect pathEffect = new CornerPathEffect(45);
paint.setPathEffect(pathEffect);
path.lineTo(event.getRawX(), event.getRawY());
canvas.drawPath(path, paint);
//
Log.i("minor",""+event.getTouchMinor());
Log.i("major",""+event.getTouchMajor());
break;
case MotionEvent.ACTION_UP:
path.reset();
break;
}
return true;
}
@Override
public void onClick(View v) {
switch(v.getId())
{
case R.id.btnClear:
canvas.drawColor(Color.WHITE);
break;
}
}
}
在这里，btnClear 是 XML 中的一个按钮，您可以从中清除画布。这是 XML
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="${relativePackage}.${activityClass}" >
<SurfaceView
android:id="@+id/sv"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<Button
android:id="@+id/btnClear"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Clear"
android:textSize="18sp"
android:textColor="#ffffff"
android:background="#555555"
android:layout_alignParentRight="true"
android:layout_alignParentBottom="true"
android:onClick="onClick" />
</RelativeLayout>
这是渲染线程...
public class RenderingThread extends Thread {
private boolean keepRunning = true;
private SurfaceHolder holder = null;
public Bitmap drawingBitmap = null;
private int width = 0, height = 0;
public RenderingThread(SurfaceHolder holder, int width, int height)
{
this.holder = holder;
this.width = width;
this.height = height;
drawingBitmap = Bitmap.createBitmap(width, height, Config.ARGB_8888);
}
public void RequestStop()
{
keepRunning = false;
interrupt();
}
@Override
public void run() {
while(keepRunning)
{
try{
Thread.sleep(30);
//
if(holder != null && drawingBitmap != null)
{
Canvas canvas = holder.lockCanvas();
if(canvas != null)
{
canvas.drawColor(Color.WHITE);
Rect src = new Rect(0, 0, drawingBitmap.getWidth(), drawingBitmap.getHeight());
Rect dst = new Rect(0, 0, width, height);
canvas.drawBitmap(drawingBitmap, src, dst, new Paint());
//
holder.unlockCanvasAndPost(canvas);
}
}
}catch(Throwable ex) {
ex.printStackTrace();
}
}
}
}
祝你好运。:)