Android开发中如何实现一个图片中叠加文字功能

public class MainActivity extends AppCompatActivity {  //图片组件  private ImageView imageView;  //位于图片中的文本组件  private TextView tvInImage;  //图片和文本的父组件  private View containerView;  //父组件的尺寸  private float imageWidth, imageHeight, imagePositionX, imagePositionY;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.image_with_text);    imageView = (ImageView) findViewById(R.id.writeText_img);    EditText editText = (EditText) findViewById(R.id.writeText_et);    tvInImage = (TextView) findViewById(R.id.writeText_image_tv);    containerView = findViewById(R.id.writeText_img_rl);    imageView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {      @Override      public void onGlobalLayout() {        imageView.getViewTreeObserver().removeOnGlobalLayoutListener(this);        imagePositionX = imageView.getX();        imagePositionY = imageView.getY();        imageWidth = imageView.getWidth();        imageHeight = imageView.getHeight();        //设置文本大小        tvInImage.setMaxWidth((int) imageWidth);      }    });    imageView.setImageBitmap(getScaledBitmap(R.mipmap.test_img));    //输入框    editText.addTextChangedListener(new TextWatcher() {      @Override      public void beforeTextChanged(CharSequence s, int start, int count, int after) {      }      @Override      public void onTextChanged(CharSequence s, int start, int before, int count) {        if (s.toString().equals("")) {          tvInImage.setVisibility(View.INVISIBLE);        } else {          tvInImage.setVisibility(View.VISIBLE);          tvInImage.setText(s);        }      }      @Override      public void afterTextChanged(Editable s) {      }    });    final GestureDetector gestureDetector = new GestureDetector(this, new SimpleGestureListenerImpl());    //移动    tvInImage.setOnTouchListener(new View.OnTouchListener() {      @Override      public boolean onTouch(View v, MotionEvent event) {        gestureDetector.onTouchEvent(event);        return true;      }    });  }  //确认，生成图片  public void confirm(View view) {    Bitmap bm = loadBitmapFromView(containerView);    String filePath = Environment.getExternalStorageDirectory() + File.separator + "image_with_text.jpg";    try {      bm.compress(Bitmap.CompressFormat.JPEG, 100, new FileOutputStream(filePath));      Toast.makeText(this, "图片已保存至：SD卡根目录/image_with_text.jpg", Toast.LENGTH_LONG).show();    } catch (FileNotFoundException e) {      e.printStackTrace();    }  }  //以图片形式获取View显示的内容（类似于截图）  public static Bitmap loadBitmapFromView(View view) {    Bitmap bitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.ARGB_8888);    Canvas canvas = new Canvas(bitmap);    view.draw(canvas);    return bitmap;  }  private int count = 0;  //tvInImage的x方向和y方向移动量  private float mDx, mDy;  //移动  private class SimpleGestureListenerImpl extends GestureDetector.SimpleOnGestureListener {    @Override    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {      //向右移动时，distanceX为负；向左移动时，distanceX为正      //向下移动时，distanceY为负；向上移动时，distanceY为正      count++;      mDx -= distanceX;      mDy -= distanceY;      //边界检查      mDx = calPosition(imagePositionX - tvInImage.getX(), imagePositionX + imageWidth - (tvInImage.getX() + tvInImage.getWidth()), mDx);      mDy = calPosition(imagePositionY - tvInImage.getY(), imagePositionY + imageHeight - (tvInImage.getY() + tvInImage.getHeight()), mDy);      //控制刷新频率      if (count % 5 == 0) {        tvInImage.setX(tvInImage.getX() + mDx);        tvInImage.setY(tvInImage.getY() + mDy);      }      return true;    }  }  //计算正确的显示位置（不能超出边界）  private float calPosition(float min, float max, float current) {    if (current < min) {      return min;    }    if (current > max) {      return max;    }    return current;  }  //获取压缩后的bitmap  private Bitmap getScaledBitmap(int resId) {    BitmapFactory.Options opt = new BitmapFactory.Options();    opt.inJustDecodeBounds = true;    BitmapFactory.decodeResource(getResources(), resId, opt);    opt.inSampleSize = Utility.calculateInSampleSize(opt, 600, 800);    opt.inJustDecodeBounds = false;    return BitmapFactory.decodeResource(getResources(), resId, opt);  }}