我试图用画布画一条线。加载 Activity 时它的值为 0，然后我有一个具有单击侦听器的 Button 来更改值并画一条线。它在模拟器中运行良好，但是当我在我的真实设备（android 版本 4.1）中运行时，画布没有改变，但我知道我点击了按钮，因为我在点击监听器中放了一个吐司。这真的很奇怪。
有没有人遇到过同样的问题？任何想法将不胜感激。
以下是我的活动：
public class MainActivity extends Activity{
private Paint paintFree = new Paint();
private Paint paintLocal = new Paint();
private Paint paintRoaming = new Paint();
private int freeUsage = 0;
private int localUsage = 0;
private int roamingUsage = 0;
private int freeBarPoints;
private int localBarPoints;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
overridePendingTransition(0, 0);
line();
((Button) findViewById(R.id.btn1)).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
freeUsage = 12;
localUsage = 1;
roamingUsage = 1;
line();
Log.i("Hit Btn1", "True");
Toast.makeText(v.getContext(), "Hit Btn1", Toast.LENGTH_SHORT).show();
}
});
}
class Draw extends View{
public Draw(Context context) {
super(context);
// TODO Auto-generated constructor stub
paintFree.setStrokeWidth(20f);
paintLocal.setStrokeWidth(20f);
paintRoaming.setStrokeWidth(20f);
if (freeUsage == 0){
paintFree.setColor(Color.GRAY);
} else {
paintFree.setColor(Color.rgb(70, 227, 78));
}
if (localUsage == 0){
paintLocal.setColor(Color.GRAY);
} else {
paintLocal.setColor(Color.rgb(238, 232, 102));
}
if (roamingUsage == 0){
paintRoaming.setColor(Color.GRAY);
} else {
paintRoaming.setColor(Color.rgb(101, 177, 231));
}
}
protected void onDraw(Canvas canvas) {
int maxBarLength = canvas.getWidth() * 4 / 5;
double totalBarPoints = freeUsage + localUsage + roamingUsage;
freeBarPoints = (int) Math.round(freeUsage * maxBarLength / totalBarPoints);
localBarPoints = (int) Math.round(localUsage * maxBarLength / totalBarPoints);
// need not compute the roaming bar points
int localStartX = 0 + Math.round(freeBarPoints);
int roamingStartX = (int) localStartX + Math.round(localBarPoints);
canvas.drawLine(0, 10, localStartX, 10, paintFree);
canvas.drawLine(localStartX, 10, roamingStartX, 10, paintLocal);
canvas.drawLine(roamingStartX, 10, maxBarLength, 10, paintRoaming);
}
}
public void line(){
Draw draw;
draw = new Draw(this);
((LinearLayout) findViewById(R.id.linear)).addView(draw);
}
}