android怎么手写展示图片

要在Android应用程序中展示手写图片，可以使用Canvas API和Bitmap类来实现。具体步骤如下：

1.在布局文件中添加一个画布View：

<com.example.handwriting.CanvasView
    android:id="@+id/canvas"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FFF"
    android:layout_gravity="center" />

2.创建一个CanvasView类，并在其中实现onDraw方法，用于绘制手写图片：

class CanvasView(context: Context, attrs: AttributeSet) : View(context, attrs) {
    
    private var path = Path()
    private val drawPaint = Paint()
    private val canvasPaint = Paint(Paint.DITHER_FLAG)
    private lateinit var canvasBitmap: Bitmap
    private lateinit var drawCanvas: Canvas

    init {
        drawPaint.apply {
            color = Color.BLACK
            isAntiAlias = true
            strokeWidth = 20f
            style = Paint.Style.STROKE
            strokeJoin = Paint.Join.ROUND
            strokeCap = Paint.Cap.ROUND
        }
    }

    override fun onDraw(canvas: Canvas) {
        canvas.drawBitmap(canvasBitmap, 0f, 0f, canvasPaint)
        canvas.drawPath(path, drawPaint)
    }

    override fun onTouchEvent(event: MotionEvent): Boolean {
        val touchX = event.x
        val touchY = event.y

        when (event.action) {
            MotionEvent.ACTION_DOWN -> {
                path.moveTo(touchX, touchY)
            }
            MotionEvent.ACTION_MOVE -> {
                path.lineTo(touchX, touchY)
            }
            MotionEvent.ACTION_UP -> {
                drawCanvas.drawPath(path, drawPaint)
                path.reset()
            }
            else -> return false
        }

        invalidate()
        return true
    }

    fun init(height: Int, width: Int) {
        canvasBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
        drawCanvas = Canvas(canvasBitmap)
    }
}

3.在Activity中获取CanvasView，并设置其高度和宽度：

val canvasView = findViewById(R.id.canvas) as CanvasView
canvasView.init(displayMetrics.heightPixels, displayMetrics.widthPixels)

4.保存手写的图片，并展示到ImageView中：

val image = canvasView.drawingCache
val imageView = findViewById(R.id.image_view) as ImageView
imageView.setImageBitmap(image)