画画板小案例

public class MainActivity extends AppCompatActivity implements View.OnClickListener {    private Paint paint;    private Bitmap bitmapC;    @SuppressLint("ClickableViewAccessibility")    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button changC = findViewById(R.id.changeColor);        changC.setOnClickListener(this);        Button bold = findViewById(R.id.bold);        bold.setOnClickListener(this);        Button save = findViewById(R.id.save);        save.setOnClickListener(this);        final ImageView iv = findViewById(R.id.iv);        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.bg);        bitmapC = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), bitmap.getConfig());        paint = new Paint();        final Canvas canvas = new Canvas(bitmapC);        canvas.drawBitmap(bitmap, new Matrix(), paint);        iv.setImageBitmap(bitmapC);        iv.setOnTouchListener(new View.OnTouchListener() {            float startX = 0;            float startY = 0;            @Override            public boolean onTouch(View v, MotionEvent event) {                int action = event.getAction();                switch (action) {                    case MotionEvent.ACTION_DOWN:                        startX = event.getX();                        startY = event.getY();                        break;                    case MotionEvent.ACTION_UP:                        break;                    case MotionEvent.ACTION_MOVE:                        float stopX = event.getX();                        float stopY = event.getY();                        canvas.drawLine(startX, startY, stopX, stopY, paint);                        iv.setImageBitmap(bitmapC);                        startX = stopX;                        startY = stopY;                        break;                }                return true;            }        });    }    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.changeColor:                paint.setColor(Color.RED);                break;            case R.id.bold:                paint.setStrokeWidth(20f);                break;            case R.id.save:                try {                    File file = new File(getFilesDir().getParent(), "dazuo.png");                    FileOutputStream fos = new FileOutputStream(file);                    boolean compress = bitmapC.compress(Bitmap.CompressFormat.PNG, 100, fos);                    if (compress) {                        Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show();                    }                } catch (FileNotFoundException e) {                    Toast.makeText(this, "保存失败", Toast.LENGTH_SHORT).show();                    e.printStackTrace();                }                break;        }    }}

代码已上传https://gitee.com/nangongyibin/Android_DrawingVersion