计时器、复习
我如何开发一个应用程序,在屏幕上以固定坐标绘制一条线,并设置 1 秒持续时间的重复计时器?计时器每滴答一声,线路就会刷新。
LineRefresh.java:
package LineRefresh.xyz.com;
import java.util.Timer;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
public class LineRefresh extends Activity {
DrawView drawView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
drawView = new DrawView(this);
drawView.setBackgroundColor(Color.WHITE);
setContentView(drawView);
}
}
DrawView.java:
package LineRefresh.xyz.com;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
public class DrawView extends View {
Paint paint = new Paint();
public DrawView(Context context) {
super(context);
}
@Override
public void onDraw(Canvas canvas) {
paint.setColor(Color.BLACK);
canvas.drawLine(50, 200, 270, 200, paint);
}
}
how do i develop an app that draws a line on screen at fixed coordinates, Setting up a repeating timer of 1 second duration? On every tick of the timer,the line refreshes.
LineRefresh.java:
package LineRefresh.xyz.com;
import java.util.Timer;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
public class LineRefresh extends Activity {
DrawView drawView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
drawView = new DrawView(this);
drawView.setBackgroundColor(Color.WHITE);
setContentView(drawView);
}
}
DrawView.java:
package LineRefresh.xyz.com;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
public class DrawView extends View {
Paint paint = new Paint();
public DrawView(Context context) {
super(context);
}
@Override
public void onDraw(Canvas canvas) {
paint.setColor(Color.BLACK);
canvas.drawLine(50, 200, 270, 200, paint);
}
}
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使用
Handler
并使用它的postDelayed()
安排绘制一条线。绘制一条线后,还安排另一个
postDelayed()
来继续此过程。Use a
Handler
and use it'spostDelayed()
to schedule drawing a line.After you draw a line also schedule another
postDelayed()
to continue this process.