如何创建一个活动，我可以在其中绘制屏幕，保存图像，并将其传输到另一个可绘制屏幕

Question

现在，我正在使用自定义视图在画布上绘制，我需要将画布（可能作为位图）保存到FileOutputStream中，然后移动到另一个具有相同功能的自定义视图。

我

不确定我是否应该使用不同的方法来实现这一点，但是无论我做什么，只要我调用startActivity（i），就会崩溃。

我的

理解是，我的自定义视图是使用 onTouch（） 绘制的，它绘制到 Path 对象上，然后调用 onDraw（canvas），它在画布上绘制路径。（如果我错了，请纠正我）。

此画布是否包含位图对象？还是每次调用onDraw都需要写入在onCreate（）期间创建的单独位图？还是我需要为每次调用 onDraw（） 创建一个新的临时位图？我已经看过很多关于这个问题的不同问答，但还没有找到理解。

这是我的主要活动：

公共类 主活动扩展活动 {

Bitmap pic;
CustomView mCustomView;
OnTouchListener touchListener;
Button eraseButton;
String [] files = { "File1.png", "File2.png", "File3.png" };
int color = Color.BLACK;
RelativeLayout layout;
private Paint paint = new Paint();
private Path path = new Path();
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    layout = (RelativeLayout) findViewById(R.id.layout);
    mCustomView = new CustomView(this);
    //layout.buildDrawingCache(); should I use this?
    layout.addView(mCustomView);
    touchListener = new OnTouchListener() {
        public boolean onTouch(View v, MotionEvent event){
            float eventX = event.getX();
            float eventY = event.getY();
            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                path.moveTo(eventX, eventY);
                break;
            case MotionEvent.ACTION_MOVE:
            case MotionEvent.ACTION_UP:
                path.lineTo(eventX, eventY);
                break;
            }
            mCustomView.invalidate();
            return true;    
        }
    };
    mCustomView.setOnTouchListener(touchListener);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}
public boolean onOptionsItemSelected(MenuItem item){
    switch (item.getItemId()) {
      case R.id.black:
          Toast.makeText(this, "You have chosen " + getResources().getString(R.string.black) + ".",
                        Toast.LENGTH_SHORT).show();
          paint.setColor(Color.BLACK);
          color = Color.BLACK;         
          break;
      case R.id.red:
          Toast.makeText(this, "You have chosen " + getResources().getString(R.string.red) + ".",
                        Toast.LENGTH_SHORT).show();
          paint.setColor(Color.RED); 
          color = Color.RED;
          break;
      case R.id.blue:
          Toast.makeText(this, "You have chosen " + getResources().getString(R.string.blue) + ".",
                        Toast.LENGTH_SHORT).show();
          paint.setColor(Color.BLUE); 
          color = Color.BLUE;
          break;
      case R.id.yellow:
          Toast.makeText(this, "You have chosen " + getResources().getString(R.string.yellow) + ".",
                        Toast.LENGTH_SHORT).show();
          paint.setColor(Color.YELLOW); 
          color = Color.YELLOW;
          break;
      case R.id.erase:
          Toast.makeText(this, "You have chosen to clear the screen. The current pen is now Black.", Toast.LENGTH_SHORT).show();
          paint.setColor(Color.BLACK);
          color = Color.BLACK;
          path.reset();
          mCustomView.invalidate();
          item.setChecked(false);
          break;
      case R.id.next:
          nextScreen(); //saves the bitmap, and call startActivity(), crashing now
          return true;
      default:
          return super.onOptionsItemSelected(item);
      }
      item.setChecked(true);
      return true;
}
public void nextScreen(){
    try {
        FileOutputStream out = openFileOutput(files[0], Context.MODE_PRIVATE);
        pic.compress(Bitmap.CompressFormat.PNG, 100, out);
        out.close();
    } catch (Exception e){
        Toast.makeText(this, e.getMessage(), Toast.LENGTH_SHORT).show();
        return;
    }
    Intent i = new Intent(this.getApplicationContext(), SecondActivity.class);
    i.putExtra("filename.png", files);
    startActivity(i);
}
public class CustomView extends View {
    public CustomView(Context context) {
        super(context);
        paint.setAntiAlias(true);
        paint.setColor(color);
        paint.setStyle(Paint.Style.STROKE);
    }
    @Override
    protected void onDraw(Canvas canvas) {
        if (pic == null){
            pic = Bitmap.createBitmap(getMeasuredWidth(), getMeasuredHeight(), Bitmap.Config.ARGB_8888); //is this correct?
        }
        canvas.drawPath(path, paint);
        canvas.drawBitmap(pic, 0, 0, paint); //is this correct?
    }
}

}

Answer 1

如果要保存视图，则应使用public Bitmap getDrawingCache ()，请参阅参考。尝试修改代码：

@Override
    protected void onDraw(Canvas canvas) {
        if (pic == null){
            pic = Bitmap.createBitmap(getMeasuredWidth(), getMeasuredHeight(), Bitmap.Config.ARGB_8888); //is this correct?
        }
        canvas.drawPath(path, paint);
        //canvas.drawBitmap(pic, 0, 0, paint); //is this correct?
    }
public void nextScreen(){
    try {
        Bitmap bitmap = mCustomView.getDrawingCache ();
        FileOutputStream out = openFileOutput(files[0], Context.MODE_PRIVATE);
        bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);
        out.close();
    } catch (Exception e){
        Toast.makeText(this, e.getMessage(), Toast.LENGTH_SHORT).show();
        return;
    }
    Intent i = new Intent(this.getApplicationContext(), SecondActivity.class);
    i.putExtra("filename.png", files);
    startActivity(i);
}