Android SDK下, 如何在程序中输出日志 以及如何查看日志.
闲话少说,直接进入正题
在程序中输出日志, 使用 android.util.Log 类.
该类提供了若干静态方法
Log.v(String tag, String msg);
Log.d(String tag, String msg);
Log.i(String tag, String msg);
Log.w(String tag, String msg);
Log.e(String tag, String msg);
分别对应 Verbose, Debug, Info, Warning,Error.
tag是一个标识,可以是任意字符串,通常可以使用类名+方法名, 主要是用来在查看日志时提供一个筛选条件.
程序运行后 并不会在 ide的控制台内输出任何信息.
如果要后查看日志 请使用
adb logcat
关于adb的更多信息请查看官方网站.
当执行 adb logcat 后会以tail方式实时显示出所有的日志信息.
这时候我们通常需要对信息进行过滤,来显示我们需要的信息, 这时候我们指定的 tag就派上了用场.
adb logcat -s MyAndroid:I
这时将只显示tag为MyAndroid,级别为I或级别高于I(Warning,Error)的日志信息.
示例代码如下:
- package com.zijun;
- import android.app.Activity;
- import android.content.Context;
- import android.graphics.Canvas;
- import android.os.Bundle;
- import android.util.Log;
- import android.view.MotionEvent;
- import android.view.View;
- public class MyAndroid extends Activity {
- protected static final String ACTIVITY_TAG="MyAndroid";
- @Override
- protected void onCreate(Bundle icicle) {
- super.onCreate(icicle);
- setContentView(new MyView(this));
- }
- public class MyView extends View {
- public MyView(Context c) {
- super(c);
- }
- @Override
- protected void onDraw(Canvas canvas) {
- }
- @Override
- public boolean onMotionEvent(MotionEvent event) {
- Log.i(MyAndroid.ACTIVITY_TAG, "=============================");
- Log.d(MyAndroid.ACTIVITY_TAG, "Haha , this is a DEBUG of MyAndroid. ");
- Log.i(MyAndroid.ACTIVITY_TAG, "Haha , this is a INFO of MyAndroid. ");
- Log.w(MyAndroid.ACTIVITY_TAG, "Haha , this is a WARNING of MyAndroid. ");
- return true;
- }
- }
- }
以上程序运行后, 在命令行执行 adb logcat -s MyAndroid:I
然后在手机模拟器的屏幕上 点击 拖动鼠标 就能看到相应的日志信息.
|
在eclipse 里选择 show view 然后选择 LogCat |
附 logcat的参数说明,这个说明比较难找 我是无意间发现的
adb logcat .....
- Usage: logcat [options] [filterspecs]
- options include:
- -s Set default filter to silent.
- Like specifying filterspec '*:s'
- -f <filename> Log to file. Default to stdout
- -r [<kbytes>] Rotate log every kbytes. (16 if unspecified). Requires -f
- -n <count> Sets max number of rotated logs to <count>, default 4
- -v <format> Sets the log print format, where <format> is one of:
- brief process tag thread raw time long
- -c clear (flush) the entire log and exit
- -d dump the log and then exit (don't block)
- -g get the size of the log's ring buffer and exit
- -b <buffer> request alternate ring buffer, defaults to 'main'
- filterspecs are a series of
- <tag>[:priority]
- where <tag> is a log component tag (or * for all) and priority is:
- V Verbose
- D Debug
- I Info
- W Warn
- E Error
- F Fatal
- S Silent (supress all output)
- '*' means '*:d' and <tag> by itself means <tag>:v
- If not specified on the commandline, filterspec is set from ANDROID_LOG_TAG
- If no filterspec is found, filter defaults to '*:I'
- If not specified with -v, format is set from ANDROID_PRINTF_LOG
- or defaults to "brief"
