我正在尝试将上下文从一个类传递到另一个类..请告诉我我做错了什么..
Draw.java
public class Draw extends View{
private Context context;
private Paint paint = null;
private Point start,end;
public Draw(Context check){
super(check);
paint();
}
protected void onDraw(Canvas canvas){
super.onDraw(canvas);
canvas.drawRect(60,60,120,120,paint);
Check check = new Check(context.getApplicationContext());
check.update();
}
public void paint(){
paint= new Paint();
paint.setColor(Color.YELLOW);
paint.setAntiAlias(true);
paint.setStyle(Paint.Style.FILL_AND_STROKE);
}
}
检查.java
public class Check {
private static Check check = null;
private Context context;
public Check(Context context){
this.context = context;
}
void update() {
Toast.makeText(context, "Context Received", Toast.LENGTH_LONG).show();
}
}
RectangleActivity.java
public class RectangleActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
Context context;
super.onCreate(savedInstanceState);
Draw draw = new Draw(this);
setContentView(draw);
}
}
请帮助我..我被这个问题困扰了好几天...
最佳答案
在你的 Draw-constructor 中,你永远不会将上下文保存到你的变量中,它应该像在 Check-constructor 中一样:
this.context = context;
否则你会得到一个null
当你到达p>
context.getApplicationContext()
这也有点没必要,传context
就够了照原样。
关于android - 有人可以指出我在下面的程序中缺少什么吗,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/9062199/