如何在android中为自定义视图创建setter和getter

Posted 2023-02-26

【中文标题】如何在android中为自定义视图创建setter和getter

【英文标题】：How to create setter and getter for a custom view in android

【发布时间】：2020-07-07 06:15:59

【问题描述】：

我正在构建一个自定义视图，该视图扩展视图并为图像获取参数。到目前为止，我一直在实现从可绘制对象和服务器（通过字符串 URL）绘制图像。

class CustomView(context: Context, attrSet: AttributeSet) : View(context)

    private var typedArray = context.obtainStyledAttributes(attrSet, R.styleable.CustomView)
    private var viewColor = typedArray.getColor(R.styleable.CustomView_viewColor, Color.WHITE)
    private var viewSize = typedArray.getDimensionPixelSize(R.styleable.CustomView_viewSize, 200)
    private var rect = Rect(50, 50, this.left+viewSize, this.top+viewSize)
    var viewImage = typedArray.getResourceId(R.styleable.CustomView_viewImage, -1)
    var imageBitmap:Bitmap?=null
    var imageString = typedArray.getString(R.styleable.CustomView_imageString)


    val radius = 100f
    var cx = 0f
    var cy = 0f
    private var paint = Paint(Paint.ANTI_ALIAS_FLAG)
    private var circlePaint = Paint(Paint.ANTI_ALIAS_FLAG)
    private var labelPaint = Paint(Paint.ANTI_ALIAS_FLAG)
    init 

        paint.color = viewColor
        circlePaint.color = Color.parseColor("#000000")
        labelPaint.color = Color.parseColor("#000000")
        typedArray.recycle()
        try 
            val iStream = URL(imageString)
            imageBitmap = BitmapFactory.decodeResource(resources, viewImage) ?: BitmapFactory.decodeStream(iStream.openStream())

        catch (e:Exception)
            Log.i("Image", "Kindly provide a valid image")
        
    

    override fun onDraw(canvas: Canvas?) 

        if(cx == 0f || cy == 0f)
            cx = (width/2).toFloat()
            cy = (height/2).toFloat()
        

        canvas?.drawRect(rect, paint)
        canvas?.drawCircle(cx, cy, radius, circlePaint)

        if (imageBitmap != null)
            canvas?.drawBitmap(imageBitmap!!, 50f, 100f, null)
        
    

我还希望能够在运行时在 xml 之外更改此值，例如在活动或片段中以使其动态化。

class MainActivity : AppCompatActivity() 

    override fun onCreate(savedInstanceState: Bundle?) 
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val url =
            "https://dyl80ryjxr1ke.cloudfront.net/external_assets/hero_examples/hair_beach_v1785392215/original.jpeg"
        customView.imageString = url
     

【参考方案1】：

在 CustomView 类中，将 init 函数中的行设置为如下所示的设置函数：

class CustomView(context: Context, attrSet: AttributeSet) : View(context) 
    //setups

    init()
    
        setupFunction(imageString)
    

    fun setupFunction(url: String) 
        paint.color = viewColor
        circlePaint.color = Color.parseColor("#000000")
        labelPaint.color = Color.parseColor("#000000")
        typedArray.recycle()
        try 
            val iStream = URL(imageString)
            imageBitmap = BitmapFactory.decodeResource(resources, viewImage)
                ?: BitmapFactory.decodeStream(iStream.openStream())

         catch (e: Exception) 
            Log.i("Image", "Kindly provide a valid image")
        
    
    onDraw()

现在 setupFunction() 可以在您每次需要时从您的 Fragment 或 Activity 中调用：

customView.setupFunction(url)

视图将根据您的需要启动。

【讨论】：

我试过这个并得到Attempt to invoke virtual method 'void com.decagon.calabashtest.CustomView.setupFunc(java.lang.String)' on a null object reference

你在哪里调用它？因为这告诉你customView尚未创建。

是的。我认为我没有在超类中包含属性集。当我这样做时，错误消失了，但图像没有改变。

ok 我认为重绘将通过在 setup 函数中调用 draw 函数来实现。我已经更新了答案

感谢您的帮助@Bita 我使用了 postInvalidate() 并且它有效。我不认为 onDraw() 会因为我必须将画布传递给它。非常感谢。