常用打印Log的工具集合

格式化log输出，主tag，子tag，线程名，类及方法，文件及行数，最后是自定义的message。
格式化json字符串输出（Gson）。
行数(MainActivity.java:14)方便查看打印位置，并且在AndroidStudio中可以直接通过点击定位到代码位置。
示例：
|LogUtilsDemo_TAG1|main|: MainActivity.onCreate(MainActivity.java:14) message1
|LogUtilsDemo_TAG2|main|: MainActivity.onCreate(MainActivity.java:15) message2

Log 输出示例

LogUtils

import android.support.annotation.NonNull;
import android.util.Log;

import java.util.HashMap;
import java.util.Locale;

public class LogUtils {
    private static String APP_TAG = "LogUtils";

    private static HashMap<String, String> sCachedTag = new HashMap<>();
    private static JsonFormatter sJsonFormatter = new DefaultFormatter();

    private LogUtils() {
        throw new UnsupportedOperationException(this.getClass().getSimpleName() + " cannot be instantiated");
    }

    public static void Init(@NonNull String appTag, @NonNull JsonFormatter formatter) {
        APP_TAG = appTag;
        sJsonFormatter = formatter;
    }

    public static void i(String message) {
        Log.i(buildTag(APP_TAG), buildMessage(message));
    }

    public static void d(String message) {
        Log.d(buildTag(APP_TAG), buildMessage(message));
    }

    public static void w(String message) {
        Log.w(buildTag(APP_TAG), buildMessage(message));
    }

    public static void e(String message) {
        Log.e(buildTag(APP_TAG), buildMessage(message));
    }

    public static void v(String message) {
        Log.v(buildTag(APP_TAG), buildMessage(message));
    }

    public static void wtf(String message) {
        Log.wtf(buildTag(APP_TAG), buildMessage(message));
    }

    public static void json(String message) {
        Log.v(buildTag(APP_TAG), buildMessage(message));
    }

    public static void i(@NonNull String tag, String message) {
        Log.i(buildTag(tag), buildMessage(message));
    }

    public static void d(@NonNull String tag, String message) {
        Log.d(buildTag(tag), buildMessage(message));
    }

    public static void w(@NonNull String tag, String message) {
        Log.w(buildTag(tag), buildMessage(message));
    }

    public static void e(@NonNull String tag, String message) {
        Log.e(buildTag(tag), buildMessage(message));
    }

    public static void v(@NonNull String tag, String message) {
        Log.v(buildTag(tag), buildMessage(message));
    }

    public static void wtf(@NonNull String tag, String message) {
        Log.wtf(buildTag(tag), buildMessage(message));
    }

    public static void json(@NonNull String tag, String content) {
        Log.v(buildTag(tag), buildMessage(formatJson(content)));
    }

    private static String buildTag(@NonNull String tag) {
        String key = String.format(Locale.US, "%s@%s", tag, Thread.currentThread().getName());

        if (!sCachedTag.containsKey(key)) {
            if (APP_TAG.equals(tag)) {
                sCachedTag.put(key, String.format(Locale.US, "|%s|%s|",
                        tag,
                        Thread.currentThread().getName()
                ));
            } else {
                sCachedTag.put(key, String.format(Locale.US, "|%s_%s|%s|",
                        APP_TAG,
                        tag,
                        Thread.currentThread().getName()
                ));
            }
        }

        return sCachedTag.get(key);
    }

    private static String buildMessage(String message) {
        StackTraceElement[] traceElements = Thread.currentThread().getStackTrace();

        if (traceElements == null || traceElements.length < 4) {
            return message;
        }
        StackTraceElement traceElement = traceElements[4];

        return String.format(Locale.US, "%s.%s(%s:%d) %s",
                traceElement.getClassName().substring(traceElement.getClassName().lastIndexOf(".") + 1),
                traceElement.getMethodName(),
                traceElement.getFileName(),
                traceElement.getLineNumber(),
                message
        );
    }

    private static String formatJson(String content) {
        return String.format(Locale.US, "\n%s", sJsonFormatter.formatJson(content));
    }

    public interface JsonFormatter {
        String formatJson(String content);
    }

    private static class DefaultFormatter implements JsonFormatter {
        @Override
        public String formatJson(String content) {
            return content;
        }
    }
}

为了减少工具的依赖，降低耦合，支持自定义JsonFormatter，通过Init()方法注入。LogUtils中实现了一个默认的Formatter，但并未对json字符串做任何处理。

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        LogUtils.Init("LogUtilsDemo", new GsonFormatter());

        LogUtils.i("TAG1", "onCreate: 1");
        LogUtils.i("TAG2", "onCreate: 2");
        LogUtils.i("TAG2", "onCreate: 3");
        LogUtils.i("TAG1", "onCreate: 4");
        LogUtils.i("TAG3", "onCreate: 5");
        LogUtils.i("TAG1", "onCreate: 6");
        LogUtils.i("LogUtilsDemo", "onCreate: 7");
        LogUtils.json("TAG1", "{\"age\":23,\"hobby\":[\"reading,writing\",\"travel\"],\"name\":{\"firstName\":\"zhang\",\"lastName\":\"san\"}} ");
        LogUtils.i("", "onCreate: 8");
        LogUtils.i(null, "onCreate: 9-1");
        LogUtils.i("null", "onCreate: 9-2");
        LogUtils.i(null, "onCreate: 9-3");
        LogUtils.i(null, null);
        LogUtils.i("onCreate: 10");
        LogUtils.i(null);
    }

Log输出样式：

I/|LogUtilsDemo_TAG1|main|: MainActivity.onCreate(MainActivity.java:15) onCreate: 1
I/|LogUtilsDemo_TAG2|main|: MainActivity.onCreate(MainActivity.java:16) onCreate: 2
I/|LogUtilsDemo_TAG2|main|: MainActivity.onCreate(MainActivity.java:17) onCreate: 3
I/|LogUtilsDemo_TAG1|main|: MainActivity.onCreate(MainActivity.java:18) onCreate: 4
I/|LogUtilsDemo_TAG3|main|: MainActivity.onCreate(MainActivity.java:19) onCreate: 5
I/|LogUtilsDemo_TAG1|main|: MainActivity.onCreate(MainActivity.java:20) onCreate: 6
I/|LogUtilsDemo|main|: MainActivity.onCreate(MainActivity.java:21) onCreate: 7
V/|LogUtilsDemo_TAG1|main|: MainActivity.onCreate(MainActivity.java:22) 
                            {
                              "age": 23,
                              "hobby": [
                                "reading,writing",
                                "travel"
                              ],
                              "name": {
                                "firstName": "zhang",
                                "lastName": "san"
                              }
                            }
I/|LogUtilsDemo_|main|: MainActivity.onCreate(MainActivity.java:23) onCreate: 8
I/|LogUtilsDemo_null|main|: MainActivity.onCreate(MainActivity.java:24) onCreate: 9-1
I/|LogUtilsDemo_null|main|: MainActivity.onCreate(MainActivity.java:25) onCreate: 9-2
I/|LogUtilsDemo_null|main|: MainActivity.onCreate(MainActivity.java:26) onCreate: 9-3
I/|LogUtilsDemo_null|main|: MainActivity.onCreate(MainActivity.java:27) null
I/|LogUtilsDemo|main|: MainActivity.onCreate(MainActivity.java:28) onCreate: 10
I/|LogUtilsDemo|main|: MainActivity.onCreate(MainActivity.java:29) null

测试代码中使用Gson实现了一个Formatter:

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonParser;

public class GsonFormatter implements LogUtils.JsonFormatter {
    @Override
    public String formatJson(String content) {
        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        JsonParser parser = new JsonParser();
        JsonElement element = parser.parse(content);
        return gson.toJson(element);
    }
}