怎么在Android应用中添加一个倒计时功能?针对这个问题,这篇文章详细介绍了相对应的分析和解答,希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。
SweepView.java:
public class SweepView extends View {
private static final int DEFAULT_WIDTH = 100;
private static final int DEFAULT_HEIGHT = 100;
private int mWidth; //这里并没卵用
private int mHeight; //这个也没卵用
private RectF rectF;
private Paint paint;
private int mColor = Color.RED;//默认颜色为红色
private float mSweep = 0; //扇形角度
public SweepView(Context context) {
super(context);
init();
}
public SweepView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public SweepView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init() {
paint = new Paint();
paint.setColor(mColor); //画笔颜色
paint.setStyle(Paint.Style.FILL); //填充
paint.setAntiAlias(true); //是否抗锯齿
}
/**
* 设置扇形颜色
* UIThred
*/
public void setColor(int color) {
this.mColor = color;
paint.setColor(mColor);
//调用onDraw重绘
invalidate();
}
/**
* 设置扇形的区域0-360
* UIThred
*/
public void setSweep(float mSweep) {
this.mSweep = mSweep;
//调用onDraw重绘
invalidate();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int resultWidth = measureWidth(widthMeasureSpec);
int resultHeight = measureHeight(heightMeasureSpec);
setMeasuredDimension(resultWidth, resultHeight);
}
/**
* 绘制的宽
* 其实里面的内容我不懂,好惭愧...我以后会弄懂的.....0.0
*/
private int measureWidth(int widthMeasureSpec) {
int size = MeasureSpec.getSize(widthMeasureSpec);
int mode = MeasureSpec.getMode(widthMeasureSpec);
int result;
if (mode == MeasureSpec.EXACTLY) {
result = size;
} else {
result = DEFAULT_WIDTH;
if (mode == MeasureSpec.AT_MOST) {
result = Math.min(size, DEFAULT_WIDTH);
}
}
return result;
}
/**
* 绘制的高
* 这里面的内容我也不懂,好惭愧...我以后会弄懂的.....0.0
*/
private int measureHeight(int heightMeasureSpec) {
int size = MeasureSpec.getSize(heightMeasureSpec);
int mode = MeasureSpec.getMode(heightMeasureSpec);
int result;
if (mode == MeasureSpec.EXACTLY) {
result = size;
} else {
result = DEFAULT_HEIGHT;
if (mode == MeasureSpec.AT_MOST) {
result = Math.min(size, DEFAULT_HEIGHT);
}
}
return result;
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
this.mHeight = h;
this.mWidth = w;
rectF = new RectF(0, 0, w, h);
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
protected void onDraw(Canvas canvas) {
//画扇形
canvas.drawArc(rectF, -90, mSweep, true, paint);
}
}
写好自定义的View,显然我们要用它,所以布局文件中声明:(不过有一点要注意的是,如果想要控制它的位置及大小,这里要用ViewGroup来包裹,通过设置ViewGroup的位置及大小来控制它,至于为什么,我也很想知道0.0)
MainActivity.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.meijun.myapplication.MainActivity">
<RelativeLayout
android:layout_centerInParent="true"
android:layout_width="20dp"
android:background="#00f"
android:layout_height="20dp">
<com.example.meijun.myapplication.SweepView
android:layout_width="wrap_content"
android:id="@+id/sweepView"
android:layout_height="wrap_content" />
</RelativeLayout>
</RelativeLayout>
最后就是在代码里来绘制动画形态的,圆形扇形倒计时了:
MainActivity.java:
public class MainActivity extends AppCompatActivity {
private SweepView sweepView;
float angle = 0;//绘制的角度
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
sweepView = (SweepView) findViewById(R.id.sweepView);
sweepView.setColor(Color.WHITE); //设置画笔颜色
sweepView.setSweep(0); //初始绘制0度
new Thread(new Runnable() {
@Override
public void run() {
while (angle <= 360) { //这里相当于绘制一个完整的圆,结合下面的3.6及50,也就是5秒钟的倒计时
angle += 3.6;
runOnUiThread(new Runnable() {
@Override
public void run() {
sweepView.setSweep(angle);
}
});
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
}
}
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