Android：屏幕上的繪圖圈

Question

我無法在屏幕上繪製圓圈。我不知道我是否正確接近，或者如果我必須使用位圖。以下是我創建的Circle類，專門爲我的規範創建一個圓。

package com.example.alex.parkinsonsdiseaseapp; 

import android.view.View; 
import android.content.Context; 
import android.graphics.Canvas; 
import android.graphics.Paint; 

public class Circle extends View { 
    private final float x; 
    private final float y; 
    private final int r; 
    private final Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG); 

    public Circle(Context context, float x, float y, int r) { 
     super(context); 
     mPaint.setColor(0x000000); 
     this.x = x; 
     this.y = y; 
     this.r = r; 
    } 

    @Override 
    protected void onDraw(Canvas canvas) { 
     super.onDraw(canvas); 
     canvas.drawCircle(x, y, r, mPaint); 
    } 
} 

下面是使用上述類的活動。

package com.example.alex.parkinsonsdiseaseapp; 

import android.app.Activity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.LinearLayout; 
import android.widget.Toast; 
import android.widget.LinearLayout.LayoutParams; 

public class FingerTappingActivity extends Activity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_finger_tapping); 

     LinearLayout circle = (LinearLayout) findViewById(R.id.lt); 
     View circleView = new Circle(this, 100, 100, 100); 
     circleView.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)); 
     circle.addView(circleView); 
     Toast.makeText(FingerTappingActivity.this, "Test", Toast.LENGTH_SHORT).show(); 

    } 
} 

Answer 1

你應該設置的LayoutParams在CircleView

View circleView = new Circle(this, 50, 50, 100) 
circleView.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)); 
circle.addView(circleView); 

Answer 2

使用所需的XML繪製，而是如果只是一個圓圈。檢查How to define a circle shape in an android xml drawable file?中的答案。

具有XML繪製後，在佈局創建一個ImageView的，幷包括爲你的Android：SRC

有了這個，你就不必擔心LayoutParam等您可以在您的ImageView的定義，並將它們相應放置在您的佈局中您喜歡的位置。

修訂

亞歷你好，根據自己的需要，我有一個生成的視圖隨機界的一個完整的代碼。

public class RandomCircles extends View { 

    public int height; 
    Context context; 
    private Paint mPaint; 

    private static final int MAX_SIZE = 200; 
    private List<Data> dataList = new ArrayList<>(); 

    public RandomCircles(Context c, AttributeSet attrs) { 
     super(c, attrs); 
     context = c; 
     mPaint = new Paint(); 
     mPaint.setAntiAlias(true); 
     mPaint.setColor(Color.BLACK); 
     mPaint.setStyle(Paint.Style.STROKE); 
     mPaint.setStrokeJoin(Paint.Join.ROUND); 
     mPaint.setStrokeWidth(4f); 

    } 

    @Override 
    protected void onSizeChanged(int w, int h, int oldw, int oldh) { 
     super.onSizeChanged(w, h, oldw, oldh); 
     for (int i = 0; i <= 50; i++) { 
      int x = (int)(Math.random() * w); 
      int y = (int)(Math.random() * h); 
      int size = (int)(Math.random() * MAX_SIZE); 
      addCircle(x, y, size); 
     } 
    } 

    @Override 
    protected void onDraw(Canvas canvas) { 
     super.onDraw(canvas); 
     for (Data data : dataList) { 
      int size = data.size; 
      mPaint.setAlpha(255 - size); 
      canvas.drawCircle(data.x, data.y, data.size, mPaint); 
     } 
    } 

    private void addCircle(float x, float y, int size) { 
     dataList.add(new Data(x, y, size)); 
    } 


    class Data { 
     public float x; 
     public float y; 
     public int size; 

     public Data(float x, float y, int size) { 
      this.x = x; 
      this.y = y; 
      this.size = size; 
     } 
    } 
} 

從它創建一個類，並在佈局中啓動它。

<com.YOU_PACKAGE_NAME.RandomCircles 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"/> 

你會得到像下面這樣的東西。雖然不完全一樣，因爲圓是隨機的。根據需要編輯代碼以滿足您的需求。乾杯。