Android--利用Java反射机制获取视频帧图像

在Android多媒体开发中，我们必须了解系统MediaScanner的整体流程，网上关于MediaScanner的文章非常多，感兴趣的朋友看以参看以下两篇博客：

http://blog.csdn.net/Innost/article/details/6083467（注重MediaScanner源码流程分析）

http://blog.csdn.net/zqiang_55/article/details/7060171（注重MediaScanner架构分析）

本文重点是怎样获取视频预览图像，并通过调用Gallery的MovieActivity播放视频，在此对MediaScanner就不做过多介绍。闲话少说，先上效果图：

                                                

在了解了Mediascanner的基本功能后，在多媒体开发中我们常用的就是MediaStore这个类，MediaStore这个类包含了手机中的Audio、Video、Images多媒体信息。有关MediaStore的相关信息，请参考Android API。接下来直接讲解代码

Utils.java（该工具类的主要作用是获得SDcard中Video信息）

package com.jony.vedioframe;

import java.util.ArrayList;

import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.provider.MediaStore;

public class Utils {

    public static ArrayList<String> getVideoData(Context context) {
        Cursor cursor = null;
        int count = 0;
        ArrayList<String> data = new ArrayList<String>();
        Uri uri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
        String[] projection = new String[] { MediaStore.Video.Media.DATA };
        try {
            cursor = context.getContentResolver().query(uri, projection, null,
                    null, MediaStore.Video.Media.DEFAULT_SORT_ORDER);
            if (cursor != null) {
                count = cursor.getCount();
                cursor.moveToFirst();
                for (int i = 0; i < count; i++) {
                    String string = cursor
                            .getString(cursor
                                    .getColumnIndexOrThrow(MediaStore.Video.Media.DATA));
                    data.add(string);
                    cursor.moveToNext();
                }
            }
        } finally {
            if (cursor != null) {
                cursor.close();
            }
        }
        return data;
    }

}

MainActivity.java（主要通过Java反射机制获得视频Frame图像）

package com.jony.vedioframe;

import java.lang.reflect.Method;
import java.util.ArrayList;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.ImageView;

public class MainActivity extends Activity {
    private Button next;
    private ImageView image;
    private ImageView play;
    private FrameLayout vedio;
    private ArrayList<String> data;
    private int count;
    private int index = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        next = (Button) findViewById(R.id.next);
        image = (ImageView) findViewById(R.id.imageview);
        play = (ImageView) findViewById(R.id.play);
        
        vedio = (FrameLayout) findViewById(R.id.vedio);
        data = Utils.getVideoData(getApplicationContext());
        count = data.size();

        next.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                    Bitmap bitmap = createVideoThumbnail(getApplicationContext(), Uri.parse(data.get(index)));
                    if (bitmap != null) {
                        vedio.setVisibility(View.VISIBLE);
                        image.setImageBitmap(bitmap);
                        image.setTag( Uri.parse(data.get(index)));
                    index++;
                    if (index == count) {
                        index = 0;
                    }
                }
            }
        });
        play.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Intent.ACTION_VIEW);
                intent.setDataAndType(Uri.parse(image.getTag().toString()), "video/3gp");
                startActivity(intent);
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    public static Bitmap createVideoThumbnail(Context context, Uri uri) {
        Bitmap bitmap = null;
        String className = "android.media.MediaMetadataRetriever";
        Object objectMediaMetadataRetriever = null;
        Method release = null;
        try {
            objectMediaMetadataRetriever = Class.forName(className)
                    .newInstance();
            Method setDataSourceMethod = Class.forName(className).getMethod(
                    "setDataSource", Context.class, Uri.class);
            setDataSourceMethod.invoke(objectMediaMetadataRetriever, context,
                    uri);
            Method getFrameAtTimeMethod = Class.forName(className).getMethod("getFrameAtTime");
            bitmap = (Bitmap) getFrameAtTimeMethod.invoke(objectMediaMetadataRetriever);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (release != null) {
                    release.invoke(objectMediaMetadataRetriever);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return bitmap;
    }
}

布局文件

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <Button 
        android:id="@+id/next"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/next"
        />
    <TextView 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="@string/prompt"
        android:textSize="10pt"
        />
    <FrameLayout
        android:id="@+id/vedio"
        android:layout_width="fill_parent"
        android:layout_height="300dip"
        android:visibility="gone"
        >
    <ImageView 
        android:id="@+id/imageview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_marginLeft="20dip"
        android:layout_marginRight="20dip"
        android:contentDescription="@string/imageview"
        />
    <ImageView 
        android:id="@+id/play"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/play"
        android:layout_gravity="center"
        android:contentDescription="@string/imageview"
        android:focusable="true"
        />
    </FrameLayout>
</LinearLayout>

源码下载：

http://download.csdn.net/detail/weihan1314/4875129