微调器下拉实现从片段调用到新意图
spinner drop down implementation called from fragment to a new intent
我有一个应用程序，我做了一个从片段启动的意图。
但是，当我单击片段中的按钮以启动我制作的客户播放器时，我的activity（这是一个意图）遇到了错误。
错误在这一行：
dropdown.setAdapter(adapter);
这是错误：
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setAdapter(android.widget.SpinnerAdapter)' on a null object reference
at blackstone.software.sunnahboxtvmenu.DuaatRadio.onCreate(DuaatRadio.java:52)
也就是上面说的那一行
我不清楚我是如何对产生错误的下拉列表进行错误编码的。
*** 让我澄清一下：下拉列表中的频道选择是在列出所有频道的数组列表（在 xml 中）中定义的。
代码中的适配器获取列表并应该填充它。但是 - 它似乎没有被填充，因此出现错误。
它在一个独立的应用程序中工作得很好，但是当我试图让它在一个片段产生的意图中工作时（点击按钮），我得到上面列出的错误。
**** 更新：完整代码 ****
这是意图的代码（完整）：
import android.annotation.TargetApi;
import android.app.Activity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.SeekBar;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;
import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import static android.R.layout.simple_spinner_dropdown_item;
import static blackstone.software.sunnahboxtvmenu.R.string.app_name;
/**
* Created by ironmantis7x on 10/26/15.
*/
public class DuaatRadio extends Activity implements AdapterView.OnItemSelectedListener, OnPreparedListener {
private MediaPlayer mediaPlayer;
public TextView songName, duration;
private double timeElapsed = 0, finalTime = 0;
private int forwardTime = 2000, backwardTime = 2000;
private Handler durationHandler = new Handler();
private SeekBar seekbar;
//String url = "http://radio.miraath.net:7000";
//String url = new String[]{"http://radio.miraath.net:7000", "http://radio.miraath.net:7010", "http://radio.miraath.net:7020", "http://radio.miraath.net:7030","http://radio.miraath.net:7040", };
String url;
TextView radioInfo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//set the layout of the Activity
setContentView(R.layout.activity_main);
Spinner dropdown = (Spinner)findViewById(R.id.spinner1);
String[] items = new String[]{"Masjid Tawheed Radio", "Masjid Rahmah Radio", "1st Muslim Mosque Radio", "Germantown Masjid Radio", "MPUBS Radio", "UK Dawah Radio"};
String[] radioDescription = new String[]{"Masjid Tawheed (Atlanta, GA) lectures", "Masjid Rahmah (New Jersey) lectures", "1st Muslim Masjid (Pittsburgh, PA) lectures", "Germantown Masjid (Philadelphia, PA) lectures", "MPUBS (Trinadad and Tabago) lectures", "UK lectures"};
ArrayAdapter<String> adapter;
adapter = new ArrayAdapter<String>(this, simple_spinner_dropdown_item, items);
dropdown.setAdapter(adapter);
dropdown.setOnItemSelectedListener(this);
int channel = Arrays.asList((getResources().getStringArray(R.array.radios_array))).indexOf(app_name);
//initialize views
initializeViews();
}
public void initializeViews(){
songName = (TextView) findViewById(R.id.songName);
radioInfo = (TextView) findViewById(R.id.radioInfo);
mediaPlayer = new MediaPlayer();
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
finalTime = mediaPlayer.getDuration();
//duration = (TextView) findViewById(R.id.songDuration);
seekbar = (SeekBar) findViewById(R.id.seekBar);
songName.setText("Dawah Radio 24-7-12");
seekbar.setMax((int) finalTime);
seekbar.setClickable(false);
}
public void onItemSelected(AdapterView<?> parent, View v, int position, long id) {
//mediaPlayer.release();
switch (position) {
case 0:
// Whatever you want to happen when the first item gets selected
//mediaPlayer.release();
//url = "http://radio.miraath.net:7000";
url = "http://api.spreaker.com/listen/episode/6883149/shoutcast?force_http=true";
radioInfo.setText("Masjid Al-tawheed Radio");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 1:
// Whatever you want to happen when the second item gets selected
//mediaPlayer.release();
url = "http://api.spreaker.com/listen/episode/6888856/shoutcast?force_http=true";
radioInfo.setText("Masjid Rahmah (New Jersey)");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 2:
// Whatever you want to happen when the thrid item gets selected
//mediaPlayer.release();
//url = "http://radio.miraath.net:7020";
url = "http://api.spreaker.com/listen/episode/6877902/shoutcast?force_http=true";
radioInfo.setText("al-Masjid al-Awwal(Pittsburgh)");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 3:
// Whatever you want to happen when the thrid item gets selected
//mediaPlayer.release();
url = "http://api.spreaker.com/listen/episode/6545744/shoutcast?force_http=true";
radioInfo.setText("Germantown Masjid (Philadelphia)");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 4:
// Whatever you want to happen when the thrid item gets selected
//mediaPlayer.release();
url = "http://mixlr.com/mpubs/showreel/those-who-rectify-themselves-and-the-people-when-the-people-become-corrupt-by-shaykh-mustafa-mubram/";
radioInfo.setText("MPUBS (Trinadad and Tabago)");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 5:
// Whatever you want to happen when the thrid item gets selected
//mediaPlayer.release();
//url = "http://radio.miraath.net:7040";
url = "http://37.59.4.122:7040";
radioInfo.setText("UK lectures");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
// play mp3 song
public void play(View view)
{
if (!mediaPlayer.isPlaying())
{
Toast.makeText(getApplicationContext(), "Radio selected. Buffering Now...", Toast.LENGTH_LONG).show();
Toast.makeText(getApplicationContext(), "This may take a few moments. Please wait ...", Toast.LENGTH_LONG).show();
}
duration = (TextView) findViewById(R.id.songDuration);
try
{
if (mediaPlayer.isPlaying())
{
mediaPlayer.stop();
mediaPlayer.reset();
//mediaPlayer.release();
mediaPlayer.setDataSource(url);
mediaPlayer.setOnPreparedListener(this);
mediaPlayer.prepareAsync();
}
else if (!mediaPlayer.isPlaying()) {
mediaPlayer.setDataSource(url);
mediaPlayer.setOnPreparedListener(this);
mediaPlayer.prepareAsync();
}
}
catch (IllegalArgumentException e)
{
Toast.makeText(getApplicationContext(), "Radio not Available. Please try again Later.", Toast.LENGTH_LONG).show();
} catch (SecurityException e) {
Toast.makeText(getApplicationContext(), "Radio not Available. Please try again Later.", Toast.LENGTH_LONG).show();
} catch (IllegalStateException e) {
Toast.makeText(getApplicationContext(), "Radio not Available. Please try again Later.", Toast.LENGTH_LONG).show();
} catch (IOException e) {
e.printStackTrace();
}
}
//handler to change seekBarTime
private Runnable updateSeekBarTime = new Runnable() {
@TargetApi(Build.VERSION_CODES.GINGERBREAD)
public void run() {
//get current position
timeElapsed = mediaPlayer.getCurrentPosition();
//set seekbar progress
seekbar.setProgress((int) timeElapsed);
//set time remaing
double timeRemaining = finalTime - timeElapsed;
duration.setText(String.format("%d min, %d sec", TimeUnit.MILLISECONDS.toMinutes((long) timeRemaining), TimeUnit.MILLISECONDS.toSeconds((long) timeRemaining) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes((long) timeRemaining))));
//repeat yourself that again in 100 miliseconds
durationHandler.postDelayed(this, 100);
}
};
// pause mp3 song
public void pause(View view) {
Toast.makeText(getApplicationContext(), "Audio Paused ...", Toast.LENGTH_LONG).show();
mediaPlayer.reset();
}
// go forward at forwardTime seconds
public void forward(View view) {
//check if we can go forward at forwardTime seconds before song endes
if ((timeElapsed + forwardTime) <= finalTime) {
timeElapsed = timeElapsed + forwardTime;
//seek to the exact second of the track
mediaPlayer.seekTo((int) timeElapsed);
}
}
// go backwards at backwardTime seconds
public void rewind(View view) {
//check if we can go back at backwardTime seconds after song starts
if ((timeElapsed - backwardTime) > 0) {
timeElapsed = timeElapsed - backwardTime;
//seek to the exact second of the track
mediaPlayer.seekTo((int) timeElapsed);
}
}
@Override
public void onPrepared(MediaPlayer mp) {
mediaPlayer.start();
timeElapsed = mediaPlayer.getCurrentPosition();
seekbar.setProgress((int) timeElapsed);
durationHandler.postDelayed(updateSeekBarTime, 100);
}
}
谢谢。
ironmantis7x
问题不在 Fragment 中，而是在 DuaatRadio Activity 代码中，
在这一行
Spinner dropdown = (Spinner)findViewById(R.id.spinner1);
您正在尝试从 activity_main 布局中获取 ID 为 spinner1 的 dropdown Spinner。但它没有在那里定义，所以它将 return null.
下一行：
dropdown.setAdapter(adapter);
您正在尝试 setAdapter null object。结果 NullPointerException.
您已在片段 class 中定义了微调器。因此，应在片段 class 中而不是 activity 中为微调器设置数据。
我有一个应用程序，我做了一个从片段启动的意图。
但是，当我单击片段中的按钮以启动我制作的客户播放器时，我的activity（这是一个意图）遇到了错误。
错误在这一行：
dropdown.setAdapter(adapter);
这是错误：
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setAdapter(android.widget.SpinnerAdapter)' on a null object reference
at blackstone.software.sunnahboxtvmenu.DuaatRadio.onCreate(DuaatRadio.java:52)
也就是上面说的那一行
我不清楚我是如何对产生错误的下拉列表进行错误编码的。
*** 让我澄清一下：下拉列表中的频道选择是在列出所有频道的数组列表（在 xml 中）中定义的。 代码中的适配器获取列表并应该填充它。但是 - 它似乎没有被填充，因此出现错误。
它在一个独立的应用程序中工作得很好，但是当我试图让它在一个片段产生的意图中工作时（点击按钮），我得到上面列出的错误。
**** 更新：完整代码 ****
这是意图的代码（完整）：
import android.annotation.TargetApi;
import android.app.Activity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.SeekBar;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;
import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import static android.R.layout.simple_spinner_dropdown_item;
import static blackstone.software.sunnahboxtvmenu.R.string.app_name;
/**
* Created by ironmantis7x on 10/26/15.
*/
public class DuaatRadio extends Activity implements AdapterView.OnItemSelectedListener, OnPreparedListener {
private MediaPlayer mediaPlayer;
public TextView songName, duration;
private double timeElapsed = 0, finalTime = 0;
private int forwardTime = 2000, backwardTime = 2000;
private Handler durationHandler = new Handler();
private SeekBar seekbar;
//String url = "http://radio.miraath.net:7000";
//String url = new String[]{"http://radio.miraath.net:7000", "http://radio.miraath.net:7010", "http://radio.miraath.net:7020", "http://radio.miraath.net:7030","http://radio.miraath.net:7040", };
String url;
TextView radioInfo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//set the layout of the Activity
setContentView(R.layout.activity_main);
Spinner dropdown = (Spinner)findViewById(R.id.spinner1);
String[] items = new String[]{"Masjid Tawheed Radio", "Masjid Rahmah Radio", "1st Muslim Mosque Radio", "Germantown Masjid Radio", "MPUBS Radio", "UK Dawah Radio"};
String[] radioDescription = new String[]{"Masjid Tawheed (Atlanta, GA) lectures", "Masjid Rahmah (New Jersey) lectures", "1st Muslim Masjid (Pittsburgh, PA) lectures", "Germantown Masjid (Philadelphia, PA) lectures", "MPUBS (Trinadad and Tabago) lectures", "UK lectures"};
ArrayAdapter<String> adapter;
adapter = new ArrayAdapter<String>(this, simple_spinner_dropdown_item, items);
dropdown.setAdapter(adapter);
dropdown.setOnItemSelectedListener(this);
int channel = Arrays.asList((getResources().getStringArray(R.array.radios_array))).indexOf(app_name);
//initialize views
initializeViews();
}
public void initializeViews(){
songName = (TextView) findViewById(R.id.songName);
radioInfo = (TextView) findViewById(R.id.radioInfo);
mediaPlayer = new MediaPlayer();
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
finalTime = mediaPlayer.getDuration();
//duration = (TextView) findViewById(R.id.songDuration);
seekbar = (SeekBar) findViewById(R.id.seekBar);
songName.setText("Dawah Radio 24-7-12");
seekbar.setMax((int) finalTime);
seekbar.setClickable(false);
}
public void onItemSelected(AdapterView<?> parent, View v, int position, long id) {
//mediaPlayer.release();
switch (position) {
case 0:
// Whatever you want to happen when the first item gets selected
//mediaPlayer.release();
//url = "http://radio.miraath.net:7000";
url = "http://api.spreaker.com/listen/episode/6883149/shoutcast?force_http=true";
radioInfo.setText("Masjid Al-tawheed Radio");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 1:
// Whatever you want to happen when the second item gets selected
//mediaPlayer.release();
url = "http://api.spreaker.com/listen/episode/6888856/shoutcast?force_http=true";
radioInfo.setText("Masjid Rahmah (New Jersey)");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 2:
// Whatever you want to happen when the thrid item gets selected
//mediaPlayer.release();
//url = "http://radio.miraath.net:7020";
url = "http://api.spreaker.com/listen/episode/6877902/shoutcast?force_http=true";
radioInfo.setText("al-Masjid al-Awwal(Pittsburgh)");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 3:
// Whatever you want to happen when the thrid item gets selected
//mediaPlayer.release();
url = "http://api.spreaker.com/listen/episode/6545744/shoutcast?force_http=true";
radioInfo.setText("Germantown Masjid (Philadelphia)");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 4:
// Whatever you want to happen when the thrid item gets selected
//mediaPlayer.release();
url = "http://mixlr.com/mpubs/showreel/those-who-rectify-themselves-and-the-people-when-the-people-become-corrupt-by-shaykh-mustafa-mubram/";
radioInfo.setText("MPUBS (Trinadad and Tabago)");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
case 5:
// Whatever you want to happen when the thrid item gets selected
//mediaPlayer.release();
//url = "http://radio.miraath.net:7040";
url = "http://37.59.4.122:7040";
radioInfo.setText("UK lectures");
Toast.makeText(getApplicationContext(), url, Toast.LENGTH_LONG).show();
break;
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
// play mp3 song
public void play(View view)
{
if (!mediaPlayer.isPlaying())
{
Toast.makeText(getApplicationContext(), "Radio selected. Buffering Now...", Toast.LENGTH_LONG).show();
Toast.makeText(getApplicationContext(), "This may take a few moments. Please wait ...", Toast.LENGTH_LONG).show();
}
duration = (TextView) findViewById(R.id.songDuration);
try
{
if (mediaPlayer.isPlaying())
{
mediaPlayer.stop();
mediaPlayer.reset();
//mediaPlayer.release();
mediaPlayer.setDataSource(url);
mediaPlayer.setOnPreparedListener(this);
mediaPlayer.prepareAsync();
}
else if (!mediaPlayer.isPlaying()) {
mediaPlayer.setDataSource(url);
mediaPlayer.setOnPreparedListener(this);
mediaPlayer.prepareAsync();
}
}
catch (IllegalArgumentException e)
{
Toast.makeText(getApplicationContext(), "Radio not Available. Please try again Later.", Toast.LENGTH_LONG).show();
} catch (SecurityException e) {
Toast.makeText(getApplicationContext(), "Radio not Available. Please try again Later.", Toast.LENGTH_LONG).show();
} catch (IllegalStateException e) {
Toast.makeText(getApplicationContext(), "Radio not Available. Please try again Later.", Toast.LENGTH_LONG).show();
} catch (IOException e) {
e.printStackTrace();
}
}
//handler to change seekBarTime
private Runnable updateSeekBarTime = new Runnable() {
@TargetApi(Build.VERSION_CODES.GINGERBREAD)
public void run() {
//get current position
timeElapsed = mediaPlayer.getCurrentPosition();
//set seekbar progress
seekbar.setProgress((int) timeElapsed);
//set time remaing
double timeRemaining = finalTime - timeElapsed;
duration.setText(String.format("%d min, %d sec", TimeUnit.MILLISECONDS.toMinutes((long) timeRemaining), TimeUnit.MILLISECONDS.toSeconds((long) timeRemaining) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes((long) timeRemaining))));
//repeat yourself that again in 100 miliseconds
durationHandler.postDelayed(this, 100);
}
};
// pause mp3 song
public void pause(View view) {
Toast.makeText(getApplicationContext(), "Audio Paused ...", Toast.LENGTH_LONG).show();
mediaPlayer.reset();
}
// go forward at forwardTime seconds
public void forward(View view) {
//check if we can go forward at forwardTime seconds before song endes
if ((timeElapsed + forwardTime) <= finalTime) {
timeElapsed = timeElapsed + forwardTime;
//seek to the exact second of the track
mediaPlayer.seekTo((int) timeElapsed);
}
}
// go backwards at backwardTime seconds
public void rewind(View view) {
//check if we can go back at backwardTime seconds after song starts
if ((timeElapsed - backwardTime) > 0) {
timeElapsed = timeElapsed - backwardTime;
//seek to the exact second of the track
mediaPlayer.seekTo((int) timeElapsed);
}
}
@Override
public void onPrepared(MediaPlayer mp) {
mediaPlayer.start();
timeElapsed = mediaPlayer.getCurrentPosition();
seekbar.setProgress((int) timeElapsed);
durationHandler.postDelayed(updateSeekBarTime, 100);
}
}
谢谢。
ironmantis7x
问题不在 Fragment 中，而是在 DuaatRadio Activity 代码中，
在这一行
Spinner dropdown = (Spinner)findViewById(R.id.spinner1);
您正在尝试从 activity_main 布局中获取 ID 为 spinner1 的 dropdown Spinner。但它没有在那里定义，所以它将 return null.
下一行：
dropdown.setAdapter(adapter);
您正在尝试 setAdapter null object。结果 NullPointerException.
您已在片段 class 中定义了微调器。因此，应在片段 class 中而不是 activity 中为微调器设置数据。