Inject external loggers (#80)

* Improve CameraLogger, add tests

* Add log docs

README.md

@@ -60,6 +60,7 @@ See below for a [list of what was done](#roadmap) and [licensing info](#contribu
 - [Other APIs](#other-apis)  
 - [Permissions Behavior](#permissions-behavior)
 - [Manifest file](#manifest-file)
+- [Logging](#logging)
 - [Roadmap](#roadmap)
 - [Device-specific issues](#device-specific-issues)
 
@@ -491,6 +492,26 @@ The library manifest file is not strict and only asks for camera permissions. Th
 
 If you don't request this feature, you can use `CameraUtils.hasCameras()` to detect if current device has cameras, and then start the camera view.
 
+## Logging
+
+`CameraView` will log a lot of interesting events related to the camera lifecycle. These are important
+to identify bugs. The default logger will simply use Android `Log` methods posting to logcat.
+
+You can attach and detach external loggers using `CameraLogger.registerLogger()`:
+
+```java
+CameraLogger.registerLogger(new Logger() {
+    @Override
+    public void log(@LogLevel int level, String tag, String message, @Nullable Throwable throwable) {
+        // For example...
+        Crashlytics.log(message);
+    }
+});
+```
+
+Make sure you enable the logger using `CameraLogger.setLogLevel(@LogLevel int)`. The default will only
+log error events.
+
 ## Roadmap
 
 This is what was done since the library was forked. I have kept the original structure, but practically all the code was changed.

cameraview/src/androidTest/java/com/otaliastudios/cameraview/CameraLoggerTest.java

@@ -4,21 +4,52 @@ package com.otaliastudios.cameraview;
 import android.support.test.filters.SmallTest;
 import android.support.test.runner.AndroidJUnit4;
 
+import org.junit.After;
+import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
 
 import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
 
 @RunWith(AndroidJUnit4.class)
 @SmallTest
 public class CameraLoggerTest extends BaseTest {
 
+    private String loggerTag = "myLogger";
+    private CameraLogger logger;
+
+    @Before
+    public void setUp() {
+        CameraLogger.setLogLevel(CameraLogger.LEVEL_VERBOSE);
+        logger = CameraLogger.create(loggerTag);
+    }
+
+    @After
+    public void tearDown() {
+        logger = null;
+    }
+
     @Test
     public void testLoggerLevels() {
-        CameraLogger logger = CameraLogger.create("logger");
-
         // Verbose
         CameraLogger.setLogLevel(CameraLogger.LEVEL_VERBOSE);
+        logger.v("v");
+        assertEquals(CameraLogger.lastMessage, "v");
+        logger.i("i");
+        assertEquals(CameraLogger.lastMessage, "i");
+        logger.w("w");
+        assertEquals(CameraLogger.lastMessage, "w");
+        logger.e("e");
+        assertEquals(CameraLogger.lastMessage, "e");
+
+        // Info
+        CameraLogger.lastMessage = null;
+        CameraLogger.setLogLevel(CameraLogger.LEVEL_INFO);
+        logger.v("v");
+        assertNull(CameraLogger.lastMessage);
         logger.i("i");
         assertEquals(CameraLogger.lastMessage, "i");
         logger.w("w");
@@ -29,6 +60,8 @@ public class CameraLoggerTest extends BaseTest {
         // Warning
         CameraLogger.lastMessage = null;
         CameraLogger.setLogLevel(CameraLogger.LEVEL_WARNING);
+        logger.v("v");
+        assertNull(CameraLogger.lastMessage);
         logger.i("i");
         assertNull(CameraLogger.lastMessage);
         logger.w("w");
@@ -39,6 +72,8 @@ public class CameraLoggerTest extends BaseTest {
         // Error
         CameraLogger.lastMessage = null;
         CameraLogger.setLogLevel(CameraLogger.LEVEL_ERROR);
+        logger.v("v");
+        assertNull(CameraLogger.lastMessage);
         logger.i("i");
         assertNull(CameraLogger.lastMessage);
         logger.w("w");
@@ -48,10 +83,51 @@ public class CameraLoggerTest extends BaseTest {
     }
 
     @Test
-    public void testLoggerObjectArray() {
+    public void testMessage() {
-        CameraLogger.setLogLevel(CameraLogger.LEVEL_VERBOSE);
-        CameraLogger logger = CameraLogger.create("logger");
         logger.i("test", "logger", 10, null);
+        assertEquals(CameraLogger.lastTag, loggerTag);
         assertEquals(CameraLogger.lastMessage, "test logger 10 null");
     }
+
+    @Test
+    public void testExternal() {
+        CameraLogger.Logger mock = mock(CameraLogger.Logger.class);
+        CameraLogger.registerLogger(mock);
+        logger.e("hey");
+        verify(mock, times(1)).log(CameraLogger.LEVEL_ERROR, loggerTag, "hey", null);
+
+        reset(mock);
+        CameraLogger.unregisterLogger(mock);
+        logger.e("hey again");
+        verify(mock, never()).log(anyInt(), anyString(), anyString(), any(Throwable.class));
+    }
+
+    @Test
+    public void testThrowable() {
+        CameraLogger.Logger mock = mock(CameraLogger.Logger.class);
+        CameraLogger.registerLogger(mock);
+
+        final Task<Throwable> task = new Task<>();
+        doAnswer(new Answer() {
+            @Override
+            public Object answer(InvocationOnMock invocation) throws Throwable {
+                Object[] args = invocation.getArguments();
+                Throwable throwable = (Throwable) args[3];
+                task.end(throwable);
+                return null;
+            }
+        }).when(mock).log(anyInt(), anyString(), anyString(), any(Throwable.class));
+
+        task.listen();
+        logger.e("Got no error.");
+        assertNull(task.await(100));
+
+        task.listen();
+        logger.e("Got error:", new RuntimeException(""));
+        assertNotNull(task.await(100));
+
+        task.listen();
+        logger.e("Got", new RuntimeException(""), "while starting");
+        assertNotNull(task.await(100));
+    }
 }

cameraview/src/main/utils/com/otaliastudios/cameraview/CameraLogger.java

@@ -1,10 +1,13 @@
 package com.otaliastudios.cameraview;
 
 import android.support.annotation.IntDef;
+import android.support.annotation.Nullable;
 import android.util.Log;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  * Utility class that can log traces and info.
@@ -12,81 +15,144 @@ import java.lang.annotation.RetentionPolicy;
 public final class CameraLogger {
 
     public final static int LEVEL_VERBOSE = 0;
-    public final static int LEVEL_WARNING = 1;
+    public final static int LEVEL_INFO = 1;
-    public final static int LEVEL_ERROR = 2;
+    public final static int LEVEL_WARNING = 2;
+    public final static int LEVEL_ERROR = 3;
 
-    @IntDef({LEVEL_VERBOSE, LEVEL_WARNING, LEVEL_ERROR})
+    /**
+     * Interface of integers representing log levels.
+     * @see #LEVEL_VERBOSE
+     * @see #LEVEL_INFO
+     * @see #LEVEL_WARNING
+     * @see #LEVEL_ERROR
+     */
+    @IntDef({LEVEL_VERBOSE, LEVEL_INFO, LEVEL_WARNING, LEVEL_ERROR})
     @Retention(RetentionPolicy.SOURCE)
-    @interface LogLevel {}
+    public @interface LogLevel {}
 
-    private static int level = LEVEL_ERROR;
+    /**
+     * A Logger can listen to internal log events
+     * and log them to different providers.
+     * The default logger will simply post to logcat.
+     */
+    public interface Logger {
 
-    public static void setLogLevel(int logLevel) {
+        /**
-        level = logLevel;
+         * Notifies that an internal log event was just triggered.
+         *
+         * @param level the log level
+         * @param tag the log tag
+         * @param message the log message
+         * @param throwable an optional throwable
+         */
+        void log(@LogLevel int level, String tag, String message, @Nullable Throwable throwable);
     }
 
     static String lastMessage;
     static String lastTag;
 
+    private static int sLevel;
+    private static List<Logger> sLoggers;
+
+    static {
+        setLogLevel(LEVEL_ERROR);
+        sLoggers = new ArrayList<>();
+        sLoggers.add(new Logger() {
+            @Override
+            public void log(int level, String tag, String message, @Nullable Throwable throwable) {
+                switch (level) {
+                    case LEVEL_VERBOSE: Log.v(tag, message, throwable); break;
+                    case LEVEL_INFO: Log.i(tag, message, throwable); break;
+                    case LEVEL_WARNING: Log.w(tag, message, throwable); break;
+                    case LEVEL_ERROR: Log.e(tag, message, throwable); break;
+                }
+            }
+        });
+    }
+
     static CameraLogger create(String tag) {
         return new CameraLogger(tag);
     }
 
-    private String mTag;
+    /**
-
+     * Sets the log sLevel for logcat events.
-    private CameraLogger(String tag) {
+     *
-        mTag = tag;
+     * @see #LEVEL_VERBOSE
+     * @see #LEVEL_INFO
+     * @see #LEVEL_WARNING
+     * @see #LEVEL_ERROR
+     * @param logLevel the desired log sLevel
+     */
+    public static void setLogLevel(@LogLevel int logLevel) {
+        sLevel = logLevel;
     }
 
-    void i(String message) {
+    /**
-        if (should(LEVEL_VERBOSE)) {
+     * Registers an external {@link Logger} for log events.
-            Log.i(mTag, message);
+     * Make sure to unregister using {@link #unregisterLogger(Logger)}.
-            lastMessage = message;
+     *
-            lastTag = mTag;
+     * @param logger logger to add
-        }
+     */
+    public static void registerLogger(Logger logger) {
+        sLoggers.add(logger);
     }
 
-    void w(String message) {
+    /**
-        if (should(LEVEL_WARNING)) {
+     * Unregisters a previously registered {@link Logger} for log events.
-            Log.w(mTag, message);
+     * This is needed in order to avoid leaks.
-            lastMessage = message;
+     *
-            lastTag = mTag;
+     * @param logger logger to remove
-        }
+     */
+    public static void unregisterLogger(Logger logger) {
+        sLoggers.remove(logger);
     }
 
-    void e(String message) {
+    private String mTag;
-        if (should(LEVEL_ERROR)) {
+
-            Log.w(mTag, message);
+    private CameraLogger(String tag) {
-            lastMessage = message;
+        mTag = tag;
-            lastTag = mTag;
-        }
     }
 
     private boolean should(int messageLevel) {
-        return level <= messageLevel;
+        return sLevel <= messageLevel && sLoggers.size() > 0;
     }
 
-    private String string(int messageLevel, Object... ofData) {
+    void v(Object... data) {
-        String message = "";
+        log(LEVEL_VERBOSE, data);
-        if (should(messageLevel)) {
-            for (Object o : ofData) {
-                message += String.valueOf(o);
-                message += " ";
-            }
-        }
-        return message.trim();
     }
 
     void i(Object... data) {
-        i(string(LEVEL_VERBOSE, data));
+        log(LEVEL_INFO, data);
     }
 
     void w(Object... data) {
-        w(string(LEVEL_WARNING, data));
+        log(LEVEL_WARNING, data);
     }
 
     void e(Object... data) {
-        e(string(LEVEL_ERROR, data));
+        log(LEVEL_ERROR, data);
+    }
+
+    private void log(@LogLevel int level, Object... data) {
+        if (!should(level)) return;
+
+        String message = "";
+        Throwable throwable = null;
+        final int size = data.length;
+        for (Object object : data) {
+            if (object instanceof Throwable) {
+                throwable = (Throwable) object;
+            }
+            message += String.valueOf(object);
+            message += " ";
+        }
+        message = message.trim();
+        for (Logger logger : sLoggers) {
+            logger.log(level, mTag, message, throwable);
+        }
+
+        lastMessage = message;
+        lastTag = mTag;
     }
 }