Android 实现简易画图板

效果如图

直接上代码

public class PaintActivity extends Activity implements OnItemSelectedListener {
	private ImageView iv;

	private Bitmap bitmap;
	private Canvas canvas;
	// 为了不让onItemtSelecter报空指针,所以在这里创建画笔对象
	private Paint paint = new Paint();

	private String[] colorsArr = { "红色", "绿色", "蓝色", "黑色", "白色" };

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.act_paint);
		Spinner sp = (Spinner) findViewById(R.id.act_paint_color_sp);
		iv = (ImageView) findViewById(R.id.act_paint_iv);

		// 创建给sp用的arrayAdapter对象
		ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
				android.R.layout.simple_spinner_item, colorsArr);
		// 设置一个更好看的下拉列表的视图资源
		adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
		// 给sp设置适配器
		sp.setAdapter(adapter);
		// 给sp设置条目选择监听器 不能使用条目点击监听器
		sp.setOnItemSelectedListener(this);

		// 给IV添加触摸监听器
		iv.setOnTouchListener(new OnTouchListener() {
			private float startX;
			private float startY;

			@Override
			public boolean onTouch(View v, MotionEvent event) {

				// switch触摸的action
				switch (event.getAction()) {

				// 按下
				case MotionEvent.ACTION_DOWN:
					// 获取按下去的坐标点
					startX = event.getX();
					startY = event.getY();
					if (bitmap == null) {
						// 创建画纸对象 参数1,2:画纸宽高,参数3:画纸质量
						bitmap = Bitmap.createBitmap(iv.getWidth(),
								iv.getHeight(), Config.ARGB_8888);
						// 创建画板对象
						canvas = new Canvas(bitmap);
						canvas.drawColor(Color.WHITE);
						// 设置画笔粗细
						paint.setStrokeWidth(5);
					}
					break;
				// 移动
				case MotionEvent.ACTION_MOVE:
					// 获取当前移动到的坐标点
					float currentX = event.getX();
					float currentY = event.getY();
					// 将起始点和当前点连线
					canvas.drawLine(startX, startY, currentX, currentY, paint);
					// 因为MOVE会多次调用,为了实现连贯效果,绘制完当前直线后将起始点进行重新赋值,把上次的结束点作 
                    // 为起始点准备下一次的绘制
					startX = currentX;
					startY = currentY;
					// 将绘制好的bitmap设置给IV显示
					iv.setImageBitmap(bitmap);

					break;
				// 抬起
				case MotionEvent.ACTION_UP:
					Log.d("tag", "up");

					break;

				}

				return true;
			}
		});

	}

	public void save(View view) throws IOException {
		if(bitmap == null) {
			Toast.makeText(this, "您还没画,不需要保存~!", Toast.LENGTH_SHORT).show();
			return;
		}
		
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy_MM_dd_HH_mm_ss");
		String format = sdf.format(new Date());

		File file = new File(Environment
				.getExternalStorageDirectory().toString()
				+ "/"
				+ format
				+ ".jpg");
		// 添加权限<uses-permission
		// android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
		FileOutputStream fos = new FileOutputStream(file);
		boolean compress = bitmap.compress(CompressFormat.JPEG, 100, fos);

		Toast.makeText(this, compress ? "成功" : "失败", Toast.LENGTH_SHORT).show();

		if(compress){
			// 给相册app发送广播,接收到后会更新图库
			Intent intent = new Intent();
			intent.setAction(Intent.ACTION_MEDIA_MOUNTED);
			intent.setData(Uri.fromFile(file));
			sendBroadcast(intent);
		}
		

	}

	public void clear(View view) {
		// 清空画纸
		bitmap = null;
		iv.setImageBitmap(bitmap);

	}

	@Override
	public void onItemSelected(AdapterView<?> parent, View view, int position,
			long id) {
		switch (position) {
		case 0:
			paint.setColor(Color.RED);
			break;
		case 1:
			paint.setColor(Color.GREEN);
			break;
		case 2:
			paint.setColor(Color.BLUE);
			break;
		case 3:
			paint.setColor(Color.BLACK);
			break;
		case 4:
			paint.setColor(Color.WHITE);
			break;

		}

	}

	@Override
	public void onNothingSelected(AdapterView<?> parent) {

	}
}