"SurfaceView控件"-出现的问题记录

发现问题:

• 1.如果直接onCreate就画画,那么会空指针
• 2.如果价格点击事件,就会回得以解决
• 3.下次和同事讨论出结果后再来更新

代码演示:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout    android:orientation="vertical"    xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="goodjobtome.com.surfaceview.MainActivity">    <Button        android:text="开始画画"        android:onClick="click"        android:layout_width="match_parent"        android:layout_height="wrap_content"/>    <SurfaceView        android:id="@+id/sv"        android:layout_width="match_parent"        android:layout_height="match_parent"/></LinearLayout>

MianActivity.java

public class MainActivity extends Activity {    private SurfaceView mSf;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //直接在这里调用就会报错,空指针        //meth();    }    //surfaceView能子在线程画画    //加上点击就得以解决,有待研究    public void click(View view) {        meth();    }    private void meth() {        mSf = (SurfaceView) findViewById(R.id.sv);        // 1.控件获取控制器;2.控制器锁定画布并得到画布;3.定义画笔;4.解锁(画布)        for (int radius = 0; radius < 300; radius+=5) {            // 1.            SurfaceHolder holder = mSf.getHolder();            // 2.            Canvas canvas = holder.lockCanvas();            // 3.            Paint paint = new Paint();            paint.setColor(Color.GREEN);            canvas.drawCircle(350, 450, radius, paint);            // 4.            holder.unlockCanvasAndPost(canvas);        }    }}

运行结果: