android - AsyncTask doInBackground 任务卡在数据库连接上

Question

连接消息显示在我的对话框中，但从未建立连接。我知道我的连接代码可以工作，所以这不是问题。

    public class Blast_Login extends Activity {

public static boolean allowLogin = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout_blast_login);
}


public void loginClicked(View view){
    Intent intent = new Intent(this,Blast_Main.class);
    EditText user = (EditText)findViewById(R.id.username);
    String username = user.toString();
    EditText pass = (EditText)findViewById(R.id.password);
    String password = pass.toString();
    new blast_dbConnect(username,password,Blast_Login.this).execute("connecting"); 
        if(allowLogin==true) startActivity(intent);


}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.blast__login, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

}

    public class blast_dbConnect extends AsyncTask<String,String,Boolean> {
String username;
String password;
Context c;
ProgressDialog pd;
public blast_dbConnect(String user,String pass,Context context){
     username = user;
     password = pass;
     c = context;
}
@Override
protected void onPreExecute(){
    pd = new ProgressDialog(c);
    pd.setMessage("starting");
    pd.show();
}
@Override
protected Boolean doInBackground(String...params) {
    boolean login = true;
    String input = params[0];
    publishProgress(input);
    try{
        Connection conn;
        Class.forName("com.mysql.jdbc.Driver").newInstance();
        conn = DriverManager.getConnection("jdbc:mysql://server/db","user","password");
        Statement stmt = conn.createStatement();
        ResultSet rs = stmt.executeQuery(String.format("select * from users where username= '%s'",username));
        if(rs.next()==true){
            String passCheck = rs.getString("password");
            System.out.println(passCheck);
            if(passCheck.equals(password)) login = true;

        }

    }
    catch(SQLException | InstantiationException | IllegalAccessException | ClassNotFoundException e){
        e.printStackTrace();
    }
    return login;
}
@Override
protected void onProgressUpdate(String...params){
    pd.setMessage(params[0]);
}

protected void onPostExecute(boolean login){
    Blast_Login.allowLogin = login;
}

}

logcat的输出如下...

01-23 12:55:29.062: I/ActivityManager(1234): START u0 {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.example.blast/.Blast_Login (has extras)} from uid 10008 on display 0
01-23 12:55:29.073: W/AudioTrack(1234): AUDIO_OUTPUT_FLAG_FAST denied by client
01-23 12:55:29.259: I/art(947): Background concurrent mark sweep GC freed 781(33KB) AllocSpace objects, 0(0B) LOS objects, 90% free, 111KB/1135KB, paused 17.159ms total 39.040ms
01-23 12:55:29.266: I/ActivityManager(1234): Start proc com.example.blast for activity com.example.blast/.Blast_Login: pid=2348 uid=10057 gids={50057, 9997, 3003} abi=x86
01-23 12:55:29.279: I/art(2348): Not late-enabling -Xcheck:jni (already on)
01-23 12:55:29.560: D/OpenGLRenderer(2348): Render dirty regions requested: true
01-23 12:55:29.567: D/(2348): HostConnection::get() New Host Connection established 0xae0dad50, tid 2348
01-23 12:55:29.634: D/Atlas(2348): Validating map...
01-23 12:55:29.710: D/(2348): HostConnection::get() New Host Connection established 0xa6c670c0, tid 2363
01-23 12:55:29.756: I/OpenGLRenderer(2348): Initialized EGL, version 1.4
01-23 12:55:29.818: D/OpenGLRenderer(2348): Enabling debug mode 0
01-23 12:55:29.855: W/EGL_emulation(2348): eglSurfaceAttrib not implemented
01-23 12:55:29.855: W/OpenGLRenderer(2348): Failed to set EGL_SWAP_BEHAVIOR on surface 0xa6c47dc0, error=EGL_SUCCESS
01-23 12:55:30.452: I/ActivityManager(1234): Displayed com.example.blast/.Blast_Login: +1s240ms
01-23 12:55:42.244: W/AudioTrack(1234): AUDIO_OUTPUT_FLAG_FAST denied by client
01-23 12:55:42.326: D/InputEventConsistencyVerifier(2348): KeyEvent: ACTION_UP but key was not down.
01-23 12:55:42.326: D/InputEventConsistencyVerifier(2348):   in android.widget.EditText{339870e1 VFED..CL .F...... 179,558-589,637 #7f090042 app:id/password}
01-23 12:55:42.326: D/InputEventConsistencyVerifier(2348):   0: sent at 1635316000000, KeyEvent { action=ACTION_UP, keyCode=KEYCODE_TAB, scanCode=15, metaState=0, flags=0x8, repeatCount=0, eventTime=1635316, downTime=1635228, deviceId=0, source=0x101 }
01-23 12:55:50.159: W/AudioTrack(1234): AUDIO_OUTPUT_FLAG_FAST denied by client
01-23 12:55:50.256: I/art(2348): Background partial concurrent mark sweep GC freed 2687(135KB) AllocSpace objects, 0(0B) LOS objects, 48% free, 1075KB/2MB, paused 5.593ms total 58.608ms
01-23 12:55:50.329: W/EGL_emulation(2348): eglSurfaceAttrib not implemented
01-23 12:55:50.329: W/OpenGLRenderer(2348): Failed to set EGL_SWAP_BEHAVIOR on surface 0xa6c47ac0, error=EGL_SUCCESS

Answer 1

您正在 AsyncTask 中执行操作，因此结果不同步。当任务真正完成时，将 allowLogin == true 时想要执行的代码移至 onPostExecute()。