多媒體和通知---《第一行代碼Android》筆記

連接真機

從4.2版本開始，開發者選項默認是隱藏的，進入“關於手機”-“版本號”那一欄連續輕點，就能開啓開發者選項。

使用通知(Notification)

當某程序希望向用戶發出一些提示信息，而該程序又不在前臺運行時，就可以使用通知。
發出一條通知後，手機最上方的狀態欄會顯示一條通知，下拉後可以看到詳細內容。

基本使用方法

package com.example.notificationtest;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.net.Uri;
import android.support.v4.app.NotificationCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import java.io.File;

public class MainActivity extends AppCompatActivity  implements View.OnClickListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button sendNotice = (Button) findViewById(R.id.send_notice);
        sendNotice.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.send_notice:
                Intent intent = new Intent(this, NotificationActivity.class);
                /**
                 * PendingIntent is one intent like Intent of delay execution.you can use getActivity(),getBroadcast() or getService() to get the object.
                 *     first parameter: the context object.
                 *     second parameter: less commonly,you can use 0.
                 *     third parameter: Intent object.
                 *     fourth parameter: make sure pendingIntent action.has four value:FLAG_ONE_SHOT/FLAG_NO_CREATE
                 *         /FLAG_CANCEL_CURRENT/FLAG_UPDATE_CURRENT.
                 */
                PendingIntent pi = PendingIntent.getActivity(this, 0, intent, 0);
                /**
                 * first step,create NotificationManager object.you can use Context.getSystemService() method to get it.
                 *     this method has one parameter to make sure obtain which one service,we use Context.NOTIFICATION_SERVICE here.
                 */
                NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
                /**
                 * second step,we use one Builder constructor to abtain Notification object,but this api is often change,so we use
                 *     support-v4.support-4 have one NotificationCompat class,use this class's constructor to get Notification object.
                 */
                Notification notification = new NotificationCompat.Builder(this)
                        .setContentTitle("This is content title")
                        .setContentText("This is content text")
                        .setWhen(System.currentTimeMillis())
                        .setSmallIcon(R.mipmap.ic_launcher)
                        .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher))
                        //set notification onclick event.parameter is one PendingIntent object.
                        .setContentIntent(pi)
                        //播放聲音，傳入一個音頻文件的uri
                        .setSound(Uri.fromFile(new File("/system/media/audio/ringtones/ringtone_021.ogg")))
                        //手機震動，傳入的參數，下標是單數時代表靜止時間，下標是雙數時代表震動時間，單位毫秒
                        .setVibrate(new long[]{0, 1000, 1000, 1000})
                        //手機LED，（顏色，亮的時間，暗的時間）
                        .setLights(Color.GREEN, 1000, 1000)
                        //使用默認的顯示效果，會使用系統默認的鈴聲、震動等效果，如果有這個，上面的聲音、震動設置就無效了
                        //.setDefaults(NotificationCompat.DEFAULT_ALL)
                        //傳入一段長文字
                        .setStyle(new NotificationCompat.BigTextStyle().bigText("Learn how to build notifications, send and sync data, and use voice actions. Get the official Android IDE and developer tools to build apps for Android."))
                        //傳入一張大圖,BitmapFactory.decodeResource()是將圖片解析成Bitmap對象。
                        // .setStyle(new NotificationCompat.BigPictureStyle().bigPicture(BitmapFactory.decodeResource(getResources(), R.drawable.big_image)))
                        /**
                         * 設置通知的重要程度，5個量級：PRIORITY_DEFAULT:默認重要程度，和不設置效果一樣；PRIORITY_MIN：最低的重要程度；PRIORITY_LOW：較低的重要程度；
                         *     PRIORITY_HIGH:較高的重要程度；PRIORITY_MAX：最高的重要程度。
                         */
                        .setPriority(NotificationCompat.PRIORITY_MAX)
                        //用戶點擊後自動取消通知
                        .setAutoCancel(true)
                        .build();
                /**
                 * third step,show the notification.
                 *     first parameter:unique identification.
                 *     second parameter:the notification object
                 */
                manager.notify(1, notification);
                break;
            default:
                break;
        }
    }

}

package com.example.notificationtest;

import android.app.NotificationManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class NotificationActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.notification_layout);
        NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        //取消通知，這裏傳入的parameter是創建notification是傳入的unique identification
        manager.cancel(1);

    }
}

調用攝像頭和相冊

package com.example.cameraalbumtest;

import android.Manifest;
import android.annotation.TargetApi;
import android.content.ContentUris;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.provider.DocumentsContract;
import android.provider.MediaStore;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {
    public static final int TAKE_PHOTO = 1;

    public static final int CHOOSE_PHOTO = 2;

    private ImageView picture;

    private Uri imageUri;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //拍照按鈕
        Button takePhoto = (Button) findViewById(R.id.take_photo);
        //相冊中選擇圖片按鈕
        Button chooseFromAlbum = (Button) findViewById(R.id.choose_from_album);
        picture = (ImageView) findViewById(R.id.picture);

        //點擊按鈕拍照
        takePhoto.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                /**
                 * 創建File對象，用於存儲拍照後的圖片，並把圖片命名爲output_image.jpg，
                 * 並把圖片放到應用關聯緩存目錄下，getExternalCacheDir()函數用於獲取這個目錄，/sdcard/Android/data/<package name>/cache
                 * 從6.0版本開始，讀寫sd卡被列爲危險權限，圖片放到其他目錄需要進行運行時權限處理，而使用應用關聯目錄則可以調過這一步。
                 */
                File outputImage = new File(getExternalCacheDir(), "output_image.jpg");

                try {
                    if (outputImage.exists()) {
                        outputImage.delete();
                    }
                    outputImage.createNewFile();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                /**
                 * 從7.0版本開始，直接使用本地真實路徑的uri被認爲是不安全的，會報FileUriExposedException錯誤。
                 */
                if (Build.VERSION.SDK_INT < 24) {
                    imageUri = Uri.fromFile(outputImage);
                } else {
                    /**
                     *
                     * FileProvider則是一種特殊的內容提供器，它使用了和內容提供器類似的機制對數據進行保護，可以選擇性得將封裝過的uri共享給外部。
                     * FileProvider.getUriForFile()方法將File對象轉換成一個封裝過的uri對象。方法有三個參數：
                     *     first parameter:context object
                     *     second parameter:任意唯一的字符串
                     *     third parameter:剛纔創建的file object
                     */
                    imageUri = FileProvider.getUriForFile(MainActivity.this, "com.example.cameraalbumtest.fileprovider", outputImage);
                }
                // 創建啓動相機程序的intent
                Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
                //拍攝的照片存儲的路徑，把uri傳進入
                intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
                //啓動活動，返回結果會返回到onActivityResult()方法中
                startActivityForResult(intent, TAKE_PHOTO);
            }
        });

        //相冊中選擇照片，打開相冊時需要運行時權限處理
        chooseFromAlbum.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(MainActivity.this, new String[]{ Manifest.permission. WRITE_EXTERNAL_STORAGE }, 1);
                } else {
                    openAlbum();
                }
            }
        });
    }

    /**
     * 具體打開相冊操作
     */
    private void openAlbum() {
        Intent intent = new Intent("android.intent.action.GET_CONTENT");
        intent.setType("image/*");
        startActivityForResult(intent, CHOOSE_PHOTO); // 打開相冊
    }

    /**
     * 相冊中選照片時運行時權限處理的回調
     */
    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case 1:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    openAlbum();
                } else {
                    Toast.makeText(this, "You denied the permission", Toast.LENGTH_SHORT).show();
                }
                break;
            default:
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        switch (requestCode) {
            //拍照的回調處理
            case TAKE_PHOTO:
                if (resultCode == RESULT_OK) {
                    try {
                        // 將拍攝的照片顯示出來
                        Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageUri));
                        picture.setImageBitmap(bitmap);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
                break;
            //相冊中選擇照片的回調處理
            case CHOOSE_PHOTO:
                if (resultCode == RESULT_OK) {
                    // 判斷手機系統版本號,因爲從4.4版本開始，選取相冊中的圖片不再返回圖片真實的uri了，而是一個封裝過的uri，需要先解析。
                    if (Build.VERSION.SDK_INT >= 19) {
                        // 4.4及以上系統使用這個方法處理圖片
                        handleImageOnKitKat(data);
                    } else {
                        // 4.4以下系統使用這個方法處理圖片
                        handleImageBeforeKitKat(data);
                    }
                }
                break;
            default:
                break;
        }
    }

    /**
     * 4.4及以上系統使用這個方法處理相冊中選擇的圖片
     * @param data
     */
    @TargetApi(19)
    private void handleImageOnKitKat(Intent data) {
        String imagePath = null;
        Uri uri = data.getData();
        Log.d("TAG", "handleImageOnKitKat: uri is " + uri);
        //解析封裝過的uri
        if (DocumentsContract.isDocumentUri(this, uri)) {
            // 如果是document類型的Uri，則通過document id處理
            String docId = DocumentsContract.getDocumentId(uri);
            if("com.android.providers.media.documents".equals(uri.getAuthority())) {
                String id = docId.split(":")[1]; // 解析出數字格式的id
                String selection = MediaStore.Images.Media._ID + "=" + id;
                imagePath = getImagePath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, selection);
            } else if ("com.android.providers.downloads.documents".equals(uri.getAuthority())) {
                Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"), Long.valueOf(docId));
                imagePath = getImagePath(contentUri, null);
            }
        } else if ("content".equalsIgnoreCase(uri.getScheme())) {
            // 如果是content類型的Uri，則使用普通方式處理
            imagePath = getImagePath(uri, null);
        } else if ("file".equalsIgnoreCase(uri.getScheme())) {
            // 如果是file類型的Uri，直接獲取圖片路徑即可
            imagePath = uri.getPath();
        }
        displayImage(imagePath); // 根據圖片路徑顯示圖片
    }

    /**
     * 4.4以下系統使用這個方法處理相冊中選擇的圖片
     * @param data
     */
    private void handleImageBeforeKitKat(Intent data) {
        Uri uri = data.getData();
        String imagePath = getImagePath(uri, null);
        displayImage(imagePath);
    }

    /**
     * 得到圖片的真實路徑
     * @param uri
     * @param selection
     * @return
     */
    private String getImagePath(Uri uri, String selection) {
        String path = null;
        // 通過Uri和selection來獲取真實的圖片路徑
        Cursor cursor = getContentResolver().query(uri, null, selection, null, null);
        if (cursor != null) {
            if (cursor.moveToFirst()) {
                path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
            }
            cursor.close();
        }
        return path;
    }

    /**
     * 展示圖片到界面上
     * @param imagePath
     */
    private void displayImage(String imagePath) {
        if (imagePath != null) {
            Bitmap bitmap = BitmapFactory.decodeFile(imagePath);
            picture.setImageBitmap(bitmap);
        } else {
            Toast.makeText(this, "failed to get image", Toast.LENGTH_SHORT).show();
        }
    }

}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.cameraalbumtest">

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <!--註冊內容提供器-->
        <!--android:authorities 值必須與FileProvider.getUriForFile()方法中第二個參數一致-->
        <provider
            android:name="android.support.v4.content.FileProvider"
            android:authorities="com.example.cameraalbumtest.fileprovider"
            android:exported="false"
            android:grantUriPermissions="true">
            <!--指定uri的共享路徑-->
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths" />
        </provider>
    </application>

</manifest>

res/xml/file_paths.xml

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <!--external-path 用來指定uri共享的，name可以隨便填，path表示共享的具體路徑，這裏設置空表示將整個sd卡進行共享-->
    <external-path name="my_images" path="" />
</paths>

播放音頻

播放音頻用MediaPlayer類。
先添加權限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

MainActivity.java

package com.example.playaudiotest;

import android.Manifest;
import android.content.pm.PackageManager;
import android.media.MediaPlayer;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import java.io.File;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

    /**
     * 播放音頻的控制類
     */
    private MediaPlayer mediaPlayer = new MediaPlayer();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button play = (Button) findViewById(R.id.play);
        Button pause = (Button) findViewById(R.id.pause);
        Button stop = (Button) findViewById(R.id.stop);
        play.setOnClickListener(this);
        pause.setOnClickListener(this);
        stop.setOnClickListener(this);
        //運行時權限
        if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{ Manifest.permission. WRITE_EXTERNAL_STORAGE }, 1);
        } else {
            initMediaPlayer(); // 初始化MediaPlayer
        }
    }

    private void initMediaPlayer() {
        try {
            //Environment.getExternalStorageDirectory()方法獲取手機內置存儲卡根目錄
            File file = new File(Environment.getExternalStorageDirectory(), "music.mp3");
            mediaPlayer.setDataSource(file.getPath()); // 指定音頻文件的路徑
            mediaPlayer.prepare(); // 讓MediaPlayer進入到準備狀態
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case 1:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    initMediaPlayer();
                } else {
                    Toast.makeText(this, "拒絕權限將無法使用程序", Toast.LENGTH_SHORT).show();
                    finish();
                }
                break;
            default:
        }
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.play:
                if (!mediaPlayer.isPlaying()) {
                    mediaPlayer.start(); // 開始播放
                }
                break;
            case R.id.pause:
                if (mediaPlayer.isPlaying()) {
                    mediaPlayer.pause(); // 暫停播放
                }
                break;
            case R.id.stop:
                if (mediaPlayer.isPlaying()) {
                    mediaPlayer.reset(); // 停止播放
                    initMediaPlayer();
                }
                break;
            default:
                break;
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (mediaPlayer != null) {
            mediaPlayer.stop();
            mediaPlayer.release();
        }
    }

}

播放視頻

播放視頻用VideoView類控制。
添加權限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

MainActivity.java

package com.example.playvideotest;

import android.Manifest;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import android.widget.VideoView;

import java.io.File;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

    private VideoView videoView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        videoView = (VideoView) findViewById(R.id.video_view);
        Button play = (Button) findViewById(R.id.play);
        Button pause = (Button) findViewById(R.id.pause);
        Button replay = (Button) findViewById(R.id.replay);
        play.setOnClickListener(this);
        pause.setOnClickListener(this);
        replay.setOnClickListener(this);
        if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{ Manifest.permission. WRITE_EXTERNAL_STORAGE }, 1);
        } else {
            initVideoPath(); // 初始化MediaPlayer
        }
    }

    private void initVideoPath() {
        File file = new File(Environment.getExternalStorageDirectory(), "movie.mp4");
        videoView.setVideoPath(file.getPath()); // 指定視頻文件的路徑
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case 1:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    initVideoPath();
                } else {
                    Toast.makeText(this, "拒絕權限將無法使用程序", Toast.LENGTH_SHORT).show();
                    finish();
                }
                break;
            default:
        }
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.play:
                if (!videoView.isPlaying()) {
                    videoView.start(); // 開始播放
                }
                break;
            case R.id.pause:
                if (videoView.isPlaying()) {
                    videoView.pause(); // 暫停播放
                }
                break;
            case R.id.replay:
                if (videoView.isPlaying()) {
                    videoView.resume(); // 重新播放
                }
                break;
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (videoView != null) {
            videoView.suspend();
        }
    }

}