Android小技巧

非常实用的计时类

class TimeCount extends CountDownTimer{
    //参数分别为为总时长，计时时间间隔
    public TimeCount(long millsInFuture, long countDownInterval){
        super(millsInFuture, countDownInterval);
    }

    @Override
    /**
     * 计时完成时触发
     */
    public void onFinish() {
        
    }

    @Override
    /**
     * 计时过程触发
     */
    public void onTick(long millisUntilFinished) {
        
    }
}

网络连接设置严苛模式

StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
        .detectDiskReads()
        .detectDiskWrites()
        .detectNetwork()   // or .detectAll() for all detectable problems
        .penaltyLog()
        .build());
StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
        .detectLeakedSqlLiteObjects()
        .detectLeakedClosableObjects()
        .penaltyLog()
        .penaltyDeath()
        .build());

解决ScrollView中ListView长度不识别问题

/**
 * 解决ScrollView布局中不识别ListView高度问题
 *
 * @param listView
 */
public void setListViewHeightBasedOnChildren(ListView listView) {
    // 获取ListView对应的Adapter
    ListAdapter listAdapter = listView.getAdapter();
    if (listAdapter == null) {
        return;
    }

    int totalHeight = 0;
    for (int i = 0, len = listAdapter.getCount(); i < len; i++) { // listAdapter.getCount()返回数据项的数目
        View listItem = listAdapter.getView(i, null, listView);
        listItem.measure(0, 0); // 计算子项View 的宽高
        totalHeight += listItem.getMeasuredHeight(); // 统计所有子项的总高度
    }

    ViewGroup.LayoutParams params = listView.getLayoutParams();
    params.height = totalHeight
            + (listView.getDividerHeight() * (listAdapter.getCount() - 1));
    // listView.getDividerHeight()获取子项间分隔符占用的高度
    // params.height最后得到整个ListView完整显示需要的高度
    listView.setLayoutParams(params);
}

双击返回

复写onBackPressed()方法

private long firstPressedTime;

@Override
public void onBackPressed() {
	if (System.currentTimeMillis() - firstPressedTime < 2000) {
		super.onBackPressed();
	} else {
		Toast.makeText(MainActivity.this, "再按一次退出", Toast.LENGTH_SHORT).show();
		firstPressedTime = System.currentTimeMillis();
	}
}