Timber原意是木材，JakeWharton大神编写的Log库，对安卓的Log进行了一层封装，让Log的处理以列表的方式处理。
核心类为Tree，Tree封装了常用的log等级
/** A facade for handling logging calls. Install instances via {@link #plant Timber.plant()}. */
public static abstract class Tree {
final ThreadLocal explicitTag = new ThreadLocal<>();
@Nullable
String getTag() {
String tag = explicitTag.get();
if (tag != null) {
explicitTag.remove();
}
return tag;
}
/** Log a verbose message with optional format args. */
public void v(String message, Object... args) {
prepareLog(Log.VERBOSE, null, message, args);
}
/** Log a verbose exception and a message with optional format args. */
public void v(Throwable t, String message, Object... args) {
prepareLog(Log.VERBOSE, t, message, args);
}
/** Log a verbose exception. */
public void v(Throwable t) {
prepareLog(Log.VERBOSE, t, null);
}
/** Log a debug message with optional format args. */
public void d(String message, Object... args) {
prepareLog(Log.DEBUG, null, message, args);
}
/** Log a debug exception and a message with optional format args. */
public void d(Throwable t, String message, Object... args) {
prepareLog(Log.DEBUG, t, message, args);
}
/** Log a debug exception. */
public void d(Throwable t) {
prepareLog(Log.DEBUG, t, null);
}
/** Log an info message with optional format args. */
public void i(String message, Object... args) {
prepareLog(Log.INFO, null, message, args);
}
/** Log an info exception and a message with optional format args. */
public void i(Throwable t, String message, Object... args) {
prepareLog(Log.INFO, t, message, args);
}
/** Log an info exception. */
public void i(Throwable t) {
prepareLog(Log.INFO, t, null);
}
/** Log a warning message with optional format args. */
public void w(String message, Object... args) {
prepareLog(Log.WARN, null, message, args);
}
/** Log a warning exception and a message with optional format args. */
public void w(Throwable t, String message, Object... args) {
prepareLog(Log.WARN, t, message, args);
}
/** Log a warning exception. */
public void w(Throwable t) {
prepareLog(Log.WARN, t, null);
}
/** Log an error message with optional format args. */
public void e(String message, Object... args) {
prepareLog(Log.ERROR, null, message, args);
}
/** Log an error exception and a message with optional format args. */
public void e(Throwable t, String message, Object... args) {
prepareLog(Log.ERROR, t, message, args);
}
/** Log an error exception. */
public void e(Throwable t) {
prepareLog(Log.ERROR, t, null);
}
/** Log an assert message with optional format args. */
public void wtf(String message, Object... args) {
prepareLog(Log.ASSERT, null, message, args);
}
/** Log an assert exception and a message with optional format args. */
public void wtf(Throwable t, String message, Object... args) {
prepareLog(Log.ASSERT, t, message, args);
}
/** Log an assert exception. */
public void wtf(Throwable t) {
prepareLog(Log.ASSERT, t, null);
}
/** Log at {@code priority} a message with optional format args. */
public void log(int priority, String message, Object... args) {
prepareLog(priority, null, message, args);
}
/** Log at {@code priority} an exception and a message with optional format args. */
public void log(int priority, Throwable t, String message, Object... args) {
prepareLog(priority, t, message, args);
}
/** Log at {@code priority} an exception. */
public void log(int priority, Throwable t) {
prepareLog(priority, t, null);
}
/**
* Return whether a message at {@code priority} should be logged.
* @deprecated use {@link #isLoggable(String, int)} instead.
*/
@Deprecated
protected boolean isLoggable(int priority) {
return true;
}
/** Return whether a message at {@code priority} or {@code tag} should be logged. */
protected boolean isLoggable(@Nullable String tag, int priority) {
//noinspection deprecation
return isLoggable(priority);
}
private void prepareLog(int priority, Throwable t, String message, Object... args) {
// Consume tag even when message is not loggable so that next message is correctly tagged.
String tag = getTag();
if (!isLoggable(tag, priority)) {
return;
}
if (message != null && message.length() == 0) {
message = null;
}
if (message == null) {
if (t == null) {
return; // Swallow message if it's null and there's no throwable.
}
message = getStackTraceString(t);
} else {
if (args != null && args.length > 0) {
message = formatMessage(message, args);
}
if (t != null) {
message += "\n" + getStackTraceString(t);
}
}
log(priority, tag, message, t);
}
/**
* Formats a log message with optional arguments.
*/
protected String formatMessage(@NotNull String message, @NotNull Object[] args) {
return String.format(message, args);
}
private String getStackTraceString(Throwable t) {
// Don't replace this with Log.getStackTraceString() - it hides
// UnknownHostException, which is not what we want.
StringWriter sw = new StringWriter(256);
PrintWriter pw = new PrintWriter(sw, false);
t.printStackTrace(pw);
pw.flush();
return sw.toString();
}
/**
* Write a log message to its destination. Called for all level-specific methods by default.
*
* @param priority Log level. See {@link Log} for constants.
* @param tag Explicit or inferred tag. May be {@code null}.
* @param message Formatted log message. May be {@code null}, but then {@code t} will not be.
* @param t Accompanying exceptions. May be {@code null}, but then {@code message} will not be.
*/
protected abstract void log(int priority, @Nullable String tag, @NotNull String message,
@Nullable Throwable t);
}
通过plant()方法添加一个Tree，这个Tree会被添加到名为FOREST的列表中，并且会同步到forestAsArray这个数组中
/** Add a new logging tree. */
@SuppressWarnings("ConstantConditions") // Validating public API contract.
public static void plant(@NotNull Tree tree) {
if (tree == null) {
throw new NullPointerException("tree == null");
}
if (tree == TREE_OF_SOULS) {
throw new IllegalArgumentException("Cannot plant Timber into itself.");
}
synchronized (FOREST) {
FOREST.add(tree);
forestAsArray = FOREST.toArray(new Tree[FOREST.size()]);
}
}
/** Adds new logging trees. */
@SuppressWarnings("ConstantConditions") // Validating public API contract.
public static void plant(@NotNull Tree... trees) {
if (trees == null) {
throw new NullPointerException("trees == null");
}
for (Tree tree : trees) {
if (tree == null) {
throw new NullPointerException("trees contains null");
}
if (tree == TREE_OF_SOULS) {
throw new IllegalArgumentException("Cannot plant Timber into itself.");
}
}
synchronized (FOREST) {
Collections.addAll(FOREST, trees);
forestAsArray = FOREST.toArray(new Tree[FOREST.size()]);
}
}
我们调用Timber.v 等log方法的时候，底层是通过TREE_OF_SOULS代理的，TREE_OF_SOULS是Tree的实现类，代理方法会遍历forestAsArray数组，执行注册的每一个Tree对应的方法
/** A {@link Tree} that delegates to all planted trees in the {@linkplain #FOREST forest}. */
private static final Tree TREE_OF_SOULS = new Tree() {
@Override public void v(String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.v(message, args);
}
}
@Override public void v(Throwable t, String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.v(t, message, args);
}
}
@Override public void v(Throwable t) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.v(t);
}
}
@Override public void d(String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.d(message, args);
}
}
@Override public void d(Throwable t, String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.d(t, message, args);
}
}
@Override public void d(Throwable t) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.d(t);
}
}
@Override public void i(String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.i(message, args);
}
}
@Override public void i(Throwable t, String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.i(t, message, args);
}
}
@Override public void i(Throwable t) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.i(t);
}
}
@Override public void w(String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.w(message, args);
}
}
@Override public void w(Throwable t, String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.w(t, message, args);
}
}
@Override public void w(Throwable t) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.w(t);
}
}
@Override public void e(String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.e(message, args);
}
}
@Override public void e(Throwable t, String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.e(t, message, args);
}
}
@Override public void e(Throwable t) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.e(t);
}
}
@Override public void wtf(String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.wtf(message, args);
}
}
@Override public void wtf(Throwable t, String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.wtf(t, message, args);
}
}
@Override public void wtf(Throwable t) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.wtf(t);
}
}
@Override public void log(int priority, String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.log(priority, message, args);
}
}
@Override public void log(int priority, Throwable t, String message, Object... args) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.log(priority, t, message, args);
}
}
@Override public void log(int priority, Throwable t) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.log(priority, t);
}
}
@Override protected void log(int priority, String tag, @NotNull String message, Throwable t) {
throw new AssertionError("Missing override for log method.");
}
};
DebugTree，Timber默认实现的用于debug包输入日志的Tree
/** A {@link Tree Tree} for debug builds. Automatically infers the tag from the calling class. */
public static class DebugTree extends Tree {
private static final int MAX_LOG_LENGTH = 4000;
private static final int MAX_TAG_LENGTH = 23;
private static final int CALL_STACK_INDEX = 5;
private static final Pattern ANONYMOUS_CLASS = Pattern.compile("(\\$\\d+)+$");
/**
* Extract the tag which should be used for the message from the {@code element}. By default
* this will use the class name without any anonymous class suffixes (e.g., {@code Foo$1}
* becomes {@code Foo}).
*
* Note: This will not be called if a {@linkplain #tag(String) manual tag} was specified.
*/
@Nullable
protected String createStackElementTag(@NotNull StackTraceElement element) {
String tag = element.getClassName();
Matcher m = ANONYMOUS_CLASS.matcher(tag);
if (m.find()) {
tag = m.replaceAll("");
}
tag = tag.substring(tag.lastIndexOf('.') + 1);
// Tag length limit was removed in API 24.
if (tag.length() <= MAX_TAG_LENGTH || Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
return tag;
}
return tag.substring(0, MAX_TAG_LENGTH);
}
@Override final String getTag() {
String tag = super.getTag();
if (tag != null) {
return tag;
}
// DO NOT switch this to Thread.getCurrentThread().getStackTrace(). The test will pass
// because Robolectric runs them on the JVM but on Android the elements are different.
StackTraceElement[] stackTrace = new Throwable().getStackTrace();
if (stackTrace.length <= CALL_STACK_INDEX) {
throw new IllegalStateException(
"Synthetic stacktrace didn't have enough elements: are you using proguard?");
}
return createStackElementTag(stackTrace[CALL_STACK_INDEX]);
}
/**
* Break up {@code message} into maximum-length chunks (if needed) and send to either
* {@link Log#println(int, String, String) Log.println()} or
* {@link Log#wtf(String, String) Log.wtf()} for logging.
*
* {@inheritDoc}
*/
@Override protected void log(int priority, String tag, @NotNull String message, Throwable t) {
if (message.length() < MAX_LOG_LENGTH) {
if (priority == Log.ASSERT) {
Log.wtf(tag, message);
} else {
Log.println(priority, tag, message);
}
return;
}
// Split by line, then ensure each line can fit into Log's maximum length.
for (int i = 0, length = message.length(); i < length; i++) {
int newline = message.indexOf('\n', i);
newline = newline != -1 ? newline : length;
do {
int end = Math.min(newline, i + MAX_LOG_LENGTH);
String part = message.substring(i, end);
if (priority == Log.ASSERT) {
Log.wtf(tag, part);
} else {
Log.println(priority, tag, part);
}
i = end;
} while (i < newline);
}
}
}
其中有个自动推断Tag的方法值得学习
// DO NOT switch this to Thread.getCurrentThread().getStackTrace(). The test will pass
// because Robolectric runs them on the JVM but on Android the elements are different.
StackTraceElement[] stackTrace = new Throwable().getStackTrace();
if (stackTrace.length <= CALL_STACK_INDEX) {
throw new IllegalStateException(
"Synthetic stacktrace didn't have enough elements: are you using proguard?");
}
return createStackElementTag(stackTrace[CALL_STACK_INDEX]);
还有个Throwable转String的方法：
private String getStackTraceString(Throwable t) {
// Don't replace this with Log.getStackTraceString() - it hides
// UnknownHostException, which is not what we want.
StringWriter sw = new StringWriter(256);
PrintWriter pw = new PrintWriter(sw, false);
t.printStackTrace(pw);
pw.flush();
return sw.toString();
}
其他方法：
tag(String tag)：设置之后的Log的tag
/** Set a one-time tag for use on the next logging call. */
@NotNull
public static Tree tag(String tag) {
Tree[] forest = forestAsArray;
for (Tree tree : forest) {
tree.explicitTag.set(tag);
}
return TREE_OF_SOULS;
}
uproot(@NotNull Tree tree)：移除一个Tree
/** Remove a planted tree. */
public static void uproot(@NotNull Tree tree) {
synchronized (FOREST) {
if (!FOREST.remove(tree)) {
throw new IllegalArgumentException("Cannot uproot tree which is not planted: " + tree);
}
forestAsArray = FOREST.toArray(new Tree[FOREST.size()]);
}
}
uprootAll()：移除所有Tree
/** Remove all planted trees. */
public static void uprootAll() {
synchronized (FOREST) {
FOREST.clear();
forestAsArray = TREE_ARRAY_EMPTY;
}
}
forest()：返回所有包含所有Tree的复制列表（该列表不能编辑）：
/** Return a copy of all planted {@linkplain Tree trees}. */
@NotNull
public static List forest() {
synchronized (FOREST) {
return unmodifiableList(new ArrayList<>(FOREST));
}
}