Question

单击列表项时，我试图将图像从列表视图传递到另一个活动。我设法弄清楚了如何从列表项中获取文本数据，但是一直停留在如何将图像从列表传递到预期活动的过程中。数据存储在包含图像作为资源的数组中。我知道我可能缺少一些琐碎的东西，但是我试图使它以多种方式工作，并查看了多个教程，但未能解决问题。

这是我的活动代码，其中声明了数组，声明了on item click监听器。

    package com.example.android.musicplayer69;

import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Parcelable;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;

import java.io.ByteArrayOutputStream;
import java.util.ArrayList;

public class ArtistActivity extends AppCompatActivity {
    public static final String KEY_SONG = "KEY_SONG";
    public static final String KEY_ARTIST = "KEY_ARTIST";





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

        ArrayList<Song> song = new ArrayList<Song>();


        /** words.add("one")*/

        song.add(new Song("Last Night", "The Strokes", "Is this 
It",R.drawable.albumcover));
        song.add(new Song("Golden Fleeces", "Israel Nash", 
"Lifted",R.drawable.play));
        song.add(new Song("Heavy, California", "Jungle", "Heavy 
California",R.drawable.albumcover));
        song.add(new Song("Grow Up", "Boiler", "Grow 
Up",R.drawable.albumcover));
        song.add(new Song("The Ballad of the Costa Concordia", "Car Seat 
Head Rest", "Teens of Denial",R.drawable.albumcover));
        song.add(new Song("Leaving", "Bass Drum of Death", "Just 
Business",R.drawable.albumcover));
        song.add(new Song("Creature Comfort", "Woods", "City Sun Eater in 
the River of Light",R.drawable.albumcover));
        song.add(new Song("Summer with Phill", "Dead Ghost", "Can't Get 
No",R.drawable.albumcover));
        song.add(new Song("Night Ride", "The Growlers", "Night 
Ride",R.drawable.albumcover));


        final SongAdapter adapter = new SongAdapter(this, song);

        ListView listView = findViewById(R.id.list);

        listView.setAdapter(adapter);


        // When listView item is clicked, item data is sent to new activity
        listView.setOnItemClickListener(new 
AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int 
position, long id) {
                Song item = adapter.getItem(position);

                Intent nowPlaying = new Intent(getApplicationContext(), 
MainActivity.class);
                nowPlaying.putExtra(KEY_SONG, item.getmSong());
                nowPlaying.putExtra(KEY_ARTIST, item.getmArtist());
                nowPlaying.putExtra("IMAGE_RES",item.getAlbumArt());



                startActivity(nowPlaying);}
        });


}


}

，这是我试图将信息传递给该活动的代码。

package com.example.android.musicplayer69;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.TextView;

import static com.example.android.musicplayer69.ArtistActivity.KEY_ARTIST;
import static com.example.android.musicplayer69.ArtistActivity.KEY_SONG;

public class MainActivity extends AppCompatActivity {
    private ImageSwitcher v;

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


        String playingSong = "";
        String playingArtist = "";



        Intent intent = getIntent();
        if (null != intent) {
            playingSong = intent.getStringExtra(KEY_SONG);
            playingArtist = intent.getStringExtra(KEY_ARTIST);



            {
            }

        }

        Bundle bundle = this.getIntent().getExtras();
        int nowPlayingArt = bundle.getInt("IMAGE_RES");



// Sets data to appropriate TextViews
        TextView playingSongText = (TextView) findViewById(R.id.Song);
        playingSongText.setText(playingSong);


        TextView playingArtistText = (TextView) findViewById(R.id.Artist);
        playingArtistText.setText(playingArtist);



        ImageView nowPlayingAlbumArt = findViewById(R.id.AlbumCover);
        nowPlayingAlbumArt.setImageResource(nowPlayingArt);




        // Sets activity_main as the layout file
        ImageView menu = findViewById(R.id.home_button);

        // creates button/ sets on click listener for Artist View
        menu.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent menuIntent = new Intent(MainActivity.this, 
menuActivity.class);`
                startActivity(menuIntent);
            }
        });


    }
}

这是我从控制台收到的错误：

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.android.musicplayer69, PID: 11885
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.musicplayer69/com.example.android.musicplayer69.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.os.Bundle.getInt(java.lang.String)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.os.Bundle.getInt(java.lang.String)' on a null object reference
        at com.example.android.musicplayer69.MainActivity.onCreate(MainActivity.java:41)
        at android.app.Activity.performCreate(Activity.java:7009)
        at android.app.Activity.performCreate(Activity.java:7000)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6494) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 
Disconnected from the target VM, address: 'localhost:8600', transport: 'socket'

Answer 1

尝试将图像转换为字节数组。看一个例子。

示例（将图像转换为字节数组）：

Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
ByteArrayOutputStream stream = new ByteArrayOutputStream();
bmp.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] byteArray = stream.toByteArray();

示例（传递您的字节数组）：

Intent intent = new Intent(this, NextActivity.class);
intent.putExtra("picture", byteArray);
startActivity(intent);

示例（获取传递的数据并转换为位图）：

Bundle extras = getIntent().getExtras();
byte[] byteArray = extras.getByteArray("picture");

Bitmap bmp = BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);
ImageView image = (ImageView) findViewById(R.id.imageView1);

image.setImageBitmap(bmp);

将图像从列表视图传递到另一个活动

1 个答案: