我是java / android开发的新手，所以请耐心等待。
我已经创建了一个应用程序作为在线课程的一部分，据说应该运行“猜猜名人游戏”。
问题是当我运行我的代码时，主要活动是完全空白的。
奇怪的是，课程中提供的应用程序运行没有问题，我已逐字逐句地遵循代码。我找到了另外一个有同样问题且无法解决问题的候选人。
日志中没有错误（我可以找到），我似乎找不到任何类似问题的帖子。
当我在清单xml中添加以下权限时，这种奇怪的行为才会出现：
<uses-permission android:name="android.permission.INTERNET" />
模拟器的屏幕截图（也在真实设备上测试）：
https://s9.postimg.org/su0gc58gf/Capture.png/
MainActivity的代码：
public class MainActivity extends Activity {
ArrayList<String> celebURLs = new ArrayList<String>();
ArrayList<String> celebNames = new ArrayList<String>();
int chosenCeleb = 0;
int locationOfCorrectAnswer = 0;
String[] answers = new String[4];
ImageView imageView;
Button button0;
Button button1;
Button button2;
Button button3;
public void celebChosen(View view) {
if (view.getTag().toString().equals(Integer.toString(locationOfCorrectAnswer))) {
Toast.makeText(getApplicationContext(), "Correct!", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getApplicationContext(), "Wrong! It was " + celebNames.get(chosenCeleb), Toast.LENGTH_LONG).show();
}
createNewQuestion();
}
public class ImageDownloader extends AsyncTask<String, Void, Bitmap> {
@Override
protected Bitmap doInBackground(String... urls) {
try {
URL url = new URL(urls[0]);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream inputStream = connection.getInputStream();
Bitmap myBitmap = BitmapFactory.decodeStream(inputStream);
return myBitmap;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
public class DownloadTask extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... urls) {
String result = "";
URL url;
HttpURLConnection urlConnection = null;
try {
url = new URL(urls[0]);
urlConnection = (HttpURLConnection) url.openConnection();
InputStream in = urlConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(in);
int data = reader.read();
while (data != -1) {
char current = (char) data;
result += current;
data = reader.read();
}
return result;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = (ImageView) findViewById(R.id.imageView);
button0 = (Button) findViewById(R.id.button1);
button1 = (Button) findViewById(R.id.button2);
button2 = (Button) findViewById(R.id.button3);
button3 = (Button) findViewById(R.id.button4);
DownloadTask task = new DownloadTask();
String result = null;
try {
result = task.execute("http://www.posh24.com/celebrities").get();
String[] splitResult = result.split("<div class=\"sidebarContainer\">");
Pattern p = Pattern.compile("<img src=\"(.*?)\"");
Matcher m = p.matcher(splitResult[0]);
while (m.find()) {
celebURLs.add(m.group(1));
}
p = Pattern.compile("alt=\"(.*?)\"");
m = p.matcher(splitResult[0]);
while (m.find()) {
celebNames.add(m.group(1));
}
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
createNewQuestion();
}
public void createNewQuestion() {
Random random = new Random();
chosenCeleb = random.nextInt(celebURLs.size());
ImageDownloader imageTask = new ImageDownloader();
Bitmap celebImage;
try {
celebImage = imageTask.execute(celebURLs.get(chosenCeleb)).get();
imageView.setImageBitmap(celebImage);
locationOfCorrectAnswer = random.nextInt(4);
int incorrectAnswerLocation;
for (int i = 0; i < 4; i++) {
if (i == locationOfCorrectAnswer) {
answers[i] = celebNames.get(chosenCeleb);
} else {
incorrectAnswerLocation = random.nextInt(celebURLs.size());
while (incorrectAnswerLocation == chosenCeleb) {
incorrectAnswerLocation = random.nextInt(celebURLs.size());
}
answers[i] = celebNames.get(incorrectAnswerLocation);
}
}
button0.setText(answers[0]);
button1.setText(answers[1]);
button2.setText(answers[2]);
button3.setText(answers[3]);
} catch (Exception e) {
e.printStackTrace();
}
}
}
日志：
08-21 20:47:46.778 835-835/? I/Choreographer: Skipped 37 frames! The application may be doing too much work on its main thread.
08-21 20:47:49.283 421-519/? W/AudioTrack: AUDIO_OUTPUT_FLAG_FAST denied by client
--------- beginning of system
08-21 20:47:49.335 421-434/? I/ActivityManager: START u0 {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.example.shenstone.guessthecelebrity2/.MainActivity (has extras)} from uid 10007 on display 0
08-21 20:47:49.614 421-433/? I/art: Background sticky concurrent mark sweep GC freed 10530(678KB) AllocSpace objects, 3(608KB) LOS objects, 12% free, 9MB/10MB, paused 4.358ms total 263.235ms
08-21 20:47:49.854 69-69/? I/art: Background concurrent mark sweep GC freed 794(33KB) AllocSpace objects, 0(0B) LOS objects, 90% free, 111KB/1135KB, paused 12.562ms total 112.418ms
08-21 20:47:49.945 421-1030/? I/ActivityManager: Start proc com.example.shenstone.guessthecelebrity2 for activity com.example.shenstone.guessthecelebrity2/.MainActivity: pid=3562 uid=10055 gids={50055, 9997, 3003} abi=armeabi-v7a
08-21 20:47:49.982 3562-3562/? I/art: Not late-enabling -Xcheck:jni (already on)
08-21 20:47:52.244 3562-3574/? W/art: Suspending all threads took: 12.799ms
08-21 20:47:52.262 3562-3574/? I/art: Background partial concurrent mark sweep GC freed 322(512KB) AllocSpace objects, 0(0B) LOS objects, 64% free, 555KB/1579KB, paused 14.923ms total 43.870ms
08-21 20:47:52.395 3562-3574/? I/art: Background sticky concurrent mark sweep GC freed 219(436KB) AllocSpace objects, 0(0B) LOS objects, 28% free, 1129KB/1579KB, paused 9.677ms total 22.436ms
08-21 20:47:52.534 3562-3574/? I/art: WaitForGcToComplete blocked for 10.763ms for cause Background
08-21 20:47:53.258 3562-3574/? I/art: Background sticky concurrent mark sweep GC freed 469(1634KB) AllocSpace objects, 0(0B) LOS objects, 58% free, 660KB/1599KB, paused 6.830ms total 31.639ms
08-21 20:47:56.495 3562-3573/? I/art: WaitForGcToComplete blocked for 21.032ms for cause HeapTrim
08-21 20:47:59.381 421-443/? W/ActivityManager: Launch timeout has expired, giving up wake lock!
08-21 20:48:00.154 3562-3574/? W/art: Suspending all threads took: 39.137ms
08-21 20:48:00.183 3562-3574/? I/art: Background partial concurrent mark sweep GC freed 108(3KB) AllocSpace objects, 57(862KB) LOS objects, 60% free, 663KB/1687KB, paused 41.100ms total 174.221ms
08-21 20:48:00.244 3562-3574/? W/art: Suspending all threads took: 10.311ms
08-21 20:48:00.255 3562-3574/? I/art: Background sticky concurrent mark sweep GC freed 53(1872B) AllocSpace objects, 30(451KB) LOS objects, 56% free, 728KB/1687KB, paused 12.216ms total 26.132ms
08-21 20:48:00.354 3562-3574/? W/art: Suspending all threads took: 9.038ms
08-21 20:48:00.415 3562-3574/? I/art: Background partial concurrent mark sweep GC freed 135(4KB) AllocSpace objects, 81(1221KB) LOS objects, 48% free, 1094KB/2MB, paused 12.238ms total 111.401ms
非常感谢任何帮助，谢谢！
答案 0 :(得分：0)
您正在使用AsyncTask但未启动它。使用execute（）方法启动异步任务。