致命异常 Main Android 空指针异常
Fatal Exception Main Android Null Pointer Exception
我用 TreeHouse 制作的这个天气应用程序有问题我在他们的论坛上问了一个问题，但无济于事。
这是我的两个有问题的文件...
主要活动
package com.megliosolutions.stormy;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.widget.ImageView;
import android.widget.TextView;
import com.squareup.okhttp.Call;
import com.squareup.okhttp.Callback;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import butterknife.ButterKnife;
import butterknife.InjectView;
public class MainActivity extends ActionBarActivity {
public static final String TAG = MainActivity.class.getSimpleName();
private CurrentWeather mCurrentWeather;
@InjectView(R.id.timeLabel) TextView mTimeLabel;
@InjectView(R.id.temperatureLabel) TextView mTemperatureLabel;
@InjectView(R.id.humidityValue) TextView mHumidityValue;
@InjectView(R.id.precipValue) TextView mPrecipValue;
@InjectView(R.id.summaryLabel) TextView mSummaryLabel;
@InjectView(R.id.iconImageView) ImageView mIconImageView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.inject(this);
String APIkey = "baab1393443251119f2e1e8fdf55f46d";
double latitude = 37.8267;
double longitude = -122.423;
String forecastUrl = "https://api.forecast.io/forecast/" + APIkey +
"/" + latitude + "," + longitude;
if (isNetworkAvailable()) {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(forecastUrl)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Request request, IOException e) {
}
@Override
public void onResponse(Response response) throws IOException {
try {
String jsonData = response.body().string();
Log.v(TAG, jsonData);
if (response.isSuccessful()) {
mCurrentWeather = getCurrentDetails(jsonData);
runOnUiThread(new Runnable() {
@Override
public void run() {
updateDisplay();
}
});
} else {
alertUserAboutError();
}
}
catch (IOException e) {
Log.e(TAG, "Exception caught: ", e);
}
catch (JSONException e){
Log.e(TAG, "JSON Exception caught: ", e);
}
}
});
}
else {
// Toast.makeText(this, getString(R.string.network_unavailable_message)
// , Toast.LENGTH_LONG).show();
alertUserNoNetwork();
}
Log.d(TAG, "MAIN UI code is running!");
}
private void updateDisplay() {
mTemperatureLabel.setText(mCurrentWeather.getTemperature() + "");
mTimeLabel.setText("At " + mCurrentWeather.getFormattedTime() + " it will be");
mHumidityValue.setText(mCurrentWeather.getHumidity() + "");
mPrecipValue.setText(mCurrentWeather.getPrecipChance() + "%");
mSummaryLabel.setText(mCurrentWeather.getSummary());
Drawable drawable = getResources().getDrawable(mCurrentWeather.getIconId());
mIconImageView.setImageDrawable(drawable);
}
private CurrentWeather getCurrentDetails(String jsonData) throws JSONException {
JSONObject forecast = new JSONObject(jsonData);
String timezone = forecast.getString("timezone");
Log.i(TAG, "From JSON: " + timezone);
JSONObject currently = forecast.getJSONObject("currently");
CurrentWeather currentWeather = new CurrentWeather();
currentWeather.setHumidity(currently.getDouble("humidity"));
currentWeather.setTime(currently.getLong("time"));
currentWeather.setIcon(currently.getString("icon"));
currentWeather.setPrecipChance(currently.getDouble("precipProbability"));
currentWeather.setSummary(currently.getString("summary"));
currentWeather.setTemperature(currently.getDouble("temperature"));
currentWeather.setTimeZone(timezone);
Log.d(TAG, currentWeather.getFormattedTime());
return new CurrentWeather();
}
private boolean isNetworkAvailable() {
ConnectivityManager manager = (ConnectivityManager)
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = manager.getActiveNetworkInfo();
boolean isAvailable = false;
if (networkInfo != null && networkInfo.isConnected()) {
isAvailable = true;
}
return isAvailable;
}
private void alertUserNoNetwork() {
NoNetworkAlertDialogFragment NoNetworkdialog = new NoNetworkAlertDialogFragment();
NoNetworkdialog.show(getFragmentManager(), "no_network_dialog");
}
private void alertUserAboutError() {
AlertDialogFragment dialog = new AlertDialogFragment();
dialog.show(getFragmentManager(), "error_dialog");
}
}
这里是CurrentWeather.java
package com.megliosolutions.stormy;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
/**
* Created by Jarvis on 6/10/15.
*/
public class CurrentWeather {
private String mIcon;
private long mTime;
private double mTemperature;
private double mHumidity;
private double mPrecipChance;
private String mSummary;
private String mTimeZone;
public String getTimeZone() {
return mTimeZone;
}
public void setTimeZone(String timeZone) {
mTimeZone = timeZone;
}
public String getFormattedTime(){
SimpleDateFormat formatter = new SimpleDateFormat("h:mm a");
formatter.setTimeZone(TimeZone.getTimeZone(getTimeZone()));
Date dateTime = new Date(getTime() * 1000);
String timeString = formatter.format(dateTime);
return timeString;
}
public String getIcon() {
return mIcon;
}
public void setIcon(String icon) {
mIcon = icon;
}
public int getIconId(){
// clear-day, clear-night, rain, snow, sleet, wind, fog, cloudy, partly-cloudy-day, or partly-cloudy-night
int iconId = R.drawable.clear_day;
if (mIcon.equals("clear-day")) {
iconId = R.drawable.clear_day;
}
else if (mIcon.equals("clear-night")) {
iconId = R.drawable.clear_night;
}
else if (mIcon.equals("rain")) {
iconId = R.drawable.rain;
}
else if (mIcon.equals("snow")) {
iconId = R.drawable.snow;
}
else if (mIcon.equals("sleet")) {
iconId = R.drawable.sleet;
}
else if (mIcon.equals("wind")) {
iconId = R.drawable.wind;
}
else if (mIcon.equals("fog")) {
iconId = R.drawable.fog;
}
else if (mIcon.equals("cloudy")) {
iconId = R.drawable.cloudy;
}
else if (mIcon.equals("partly-cloudy-day")) {
iconId = R.drawable.partly_cloudy;
}
else if (mIcon.equals("partly-cloudy-night")) {
iconId = R.drawable.cloudy_night;
}
return iconId;
}
public long getTime() {
return mTime;
}
public void setTime(long time) {
mTime = time;
}
public int getTemperature() {
//returns long value so either turn to long or cast int
return (int)Math.round(mTemperature);
}
public void setTemperature(double temperature) {
mTemperature = temperature;
}
public double getHumidity() {
return mHumidity;
}
public void setHumidity(double humidity) {
mHumidity = humidity;
}
public int getPrecipChance() {
double precipPercentage = mPrecipChance * 100;
return (int)Math.round(precipPercentage);
}
public void setPrecipChance(double precipChance) {
mPrecipChance = precipChance;
}
public String getSummary() {
return mSummary;
}
public void setSummary(String summary) {
mSummary = summary;
}
}
遇到空指针异常问题
06-17 00:30:14.013 6766-6766/com.megliosolutions.stormy E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.megliosolutions.stormy, PID: 6766
java.lang.NullPointerException: id == null
at java.util.TimeZone.getTimeZone(TimeZone.java:349)
at com.megliosolutions.stormy.CurrentWeather.getFormattedTime(CurrentWeather.java:30)
at com.megliosolutions.stormy.MainActivity.updateDisplay(MainActivity.java:108)
at com.megliosolutions.stormy.MainActivity.access0(MainActivity.java:28)
at com.megliosolutions.stormy.MainActivity.run(MainActivity.java:77)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
以上是我得到的错误。不知道从哪里开始。
有帮助吗？？
错误在这个函数中
public String getTimeZone() {
return mTimeZone;
}
返回null中的mTimeZone变量，所以，下面的代码引发异常：
TimeZone.getTimeZone(getTimeZone())
此外，在这个函数中：
private CurrentWeather getCurrentDetails(String jsonData) throws JSONException {
JSONObject forecast = new JSONObject(jsonData);
String timezone = forecast.getString("timezone");
Log.i(TAG, "From JSON: " + timezone);
JSONObject currently = forecast.getJSONObject("currently");
CurrentWeather currentWeather = new CurrentWeather();
currentWeather.setHumidity(currently.getDouble("humidity"));
currentWeather.setTime(currently.getLong("time"));
currentWeather.setIcon(currently.getString("icon"));
currentWeather.setPrecipChance(currently.getDouble("precipProbability"));
currentWeather.setSummary(currently.getString("summary"));
currentWeather.setTemperature(currently.getDouble("temperature"));
currentWeather.setTimeZone(timezone);
Log.d(TAG, currentWeather.getFormattedTime());
return new CurrentWeather();
}
您正在返回一个 new CurrentWeather() 对象。将其更改为：
return currentWeather;
我用 TreeHouse 制作的这个天气应用程序有问题我在他们的论坛上问了一个问题，但无济于事。
这是我的两个有问题的文件...
主要活动
package com.megliosolutions.stormy;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.widget.ImageView;
import android.widget.TextView;
import com.squareup.okhttp.Call;
import com.squareup.okhttp.Callback;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import butterknife.ButterKnife;
import butterknife.InjectView;
public class MainActivity extends ActionBarActivity {
public static final String TAG = MainActivity.class.getSimpleName();
private CurrentWeather mCurrentWeather;
@InjectView(R.id.timeLabel) TextView mTimeLabel;
@InjectView(R.id.temperatureLabel) TextView mTemperatureLabel;
@InjectView(R.id.humidityValue) TextView mHumidityValue;
@InjectView(R.id.precipValue) TextView mPrecipValue;
@InjectView(R.id.summaryLabel) TextView mSummaryLabel;
@InjectView(R.id.iconImageView) ImageView mIconImageView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.inject(this);
String APIkey = "baab1393443251119f2e1e8fdf55f46d";
double latitude = 37.8267;
double longitude = -122.423;
String forecastUrl = "https://api.forecast.io/forecast/" + APIkey +
"/" + latitude + "," + longitude;
if (isNetworkAvailable()) {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(forecastUrl)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Request request, IOException e) {
}
@Override
public void onResponse(Response response) throws IOException {
try {
String jsonData = response.body().string();
Log.v(TAG, jsonData);
if (response.isSuccessful()) {
mCurrentWeather = getCurrentDetails(jsonData);
runOnUiThread(new Runnable() {
@Override
public void run() {
updateDisplay();
}
});
} else {
alertUserAboutError();
}
}
catch (IOException e) {
Log.e(TAG, "Exception caught: ", e);
}
catch (JSONException e){
Log.e(TAG, "JSON Exception caught: ", e);
}
}
});
}
else {
// Toast.makeText(this, getString(R.string.network_unavailable_message)
// , Toast.LENGTH_LONG).show();
alertUserNoNetwork();
}
Log.d(TAG, "MAIN UI code is running!");
}
private void updateDisplay() {
mTemperatureLabel.setText(mCurrentWeather.getTemperature() + "");
mTimeLabel.setText("At " + mCurrentWeather.getFormattedTime() + " it will be");
mHumidityValue.setText(mCurrentWeather.getHumidity() + "");
mPrecipValue.setText(mCurrentWeather.getPrecipChance() + "%");
mSummaryLabel.setText(mCurrentWeather.getSummary());
Drawable drawable = getResources().getDrawable(mCurrentWeather.getIconId());
mIconImageView.setImageDrawable(drawable);
}
private CurrentWeather getCurrentDetails(String jsonData) throws JSONException {
JSONObject forecast = new JSONObject(jsonData);
String timezone = forecast.getString("timezone");
Log.i(TAG, "From JSON: " + timezone);
JSONObject currently = forecast.getJSONObject("currently");
CurrentWeather currentWeather = new CurrentWeather();
currentWeather.setHumidity(currently.getDouble("humidity"));
currentWeather.setTime(currently.getLong("time"));
currentWeather.setIcon(currently.getString("icon"));
currentWeather.setPrecipChance(currently.getDouble("precipProbability"));
currentWeather.setSummary(currently.getString("summary"));
currentWeather.setTemperature(currently.getDouble("temperature"));
currentWeather.setTimeZone(timezone);
Log.d(TAG, currentWeather.getFormattedTime());
return new CurrentWeather();
}
private boolean isNetworkAvailable() {
ConnectivityManager manager = (ConnectivityManager)
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = manager.getActiveNetworkInfo();
boolean isAvailable = false;
if (networkInfo != null && networkInfo.isConnected()) {
isAvailable = true;
}
return isAvailable;
}
private void alertUserNoNetwork() {
NoNetworkAlertDialogFragment NoNetworkdialog = new NoNetworkAlertDialogFragment();
NoNetworkdialog.show(getFragmentManager(), "no_network_dialog");
}
private void alertUserAboutError() {
AlertDialogFragment dialog = new AlertDialogFragment();
dialog.show(getFragmentManager(), "error_dialog");
}
}
这里是CurrentWeather.java
package com.megliosolutions.stormy;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
/**
* Created by Jarvis on 6/10/15.
*/
public class CurrentWeather {
private String mIcon;
private long mTime;
private double mTemperature;
private double mHumidity;
private double mPrecipChance;
private String mSummary;
private String mTimeZone;
public String getTimeZone() {
return mTimeZone;
}
public void setTimeZone(String timeZone) {
mTimeZone = timeZone;
}
public String getFormattedTime(){
SimpleDateFormat formatter = new SimpleDateFormat("h:mm a");
formatter.setTimeZone(TimeZone.getTimeZone(getTimeZone()));
Date dateTime = new Date(getTime() * 1000);
String timeString = formatter.format(dateTime);
return timeString;
}
public String getIcon() {
return mIcon;
}
public void setIcon(String icon) {
mIcon = icon;
}
public int getIconId(){
// clear-day, clear-night, rain, snow, sleet, wind, fog, cloudy, partly-cloudy-day, or partly-cloudy-night
int iconId = R.drawable.clear_day;
if (mIcon.equals("clear-day")) {
iconId = R.drawable.clear_day;
}
else if (mIcon.equals("clear-night")) {
iconId = R.drawable.clear_night;
}
else if (mIcon.equals("rain")) {
iconId = R.drawable.rain;
}
else if (mIcon.equals("snow")) {
iconId = R.drawable.snow;
}
else if (mIcon.equals("sleet")) {
iconId = R.drawable.sleet;
}
else if (mIcon.equals("wind")) {
iconId = R.drawable.wind;
}
else if (mIcon.equals("fog")) {
iconId = R.drawable.fog;
}
else if (mIcon.equals("cloudy")) {
iconId = R.drawable.cloudy;
}
else if (mIcon.equals("partly-cloudy-day")) {
iconId = R.drawable.partly_cloudy;
}
else if (mIcon.equals("partly-cloudy-night")) {
iconId = R.drawable.cloudy_night;
}
return iconId;
}
public long getTime() {
return mTime;
}
public void setTime(long time) {
mTime = time;
}
public int getTemperature() {
//returns long value so either turn to long or cast int
return (int)Math.round(mTemperature);
}
public void setTemperature(double temperature) {
mTemperature = temperature;
}
public double getHumidity() {
return mHumidity;
}
public void setHumidity(double humidity) {
mHumidity = humidity;
}
public int getPrecipChance() {
double precipPercentage = mPrecipChance * 100;
return (int)Math.round(precipPercentage);
}
public void setPrecipChance(double precipChance) {
mPrecipChance = precipChance;
}
public String getSummary() {
return mSummary;
}
public void setSummary(String summary) {
mSummary = summary;
}
}
遇到空指针异常问题
06-17 00:30:14.013 6766-6766/com.megliosolutions.stormy E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.megliosolutions.stormy, PID: 6766
java.lang.NullPointerException: id == null
at java.util.TimeZone.getTimeZone(TimeZone.java:349)
at com.megliosolutions.stormy.CurrentWeather.getFormattedTime(CurrentWeather.java:30)
at com.megliosolutions.stormy.MainActivity.updateDisplay(MainActivity.java:108)
at com.megliosolutions.stormy.MainActivity.access0(MainActivity.java:28)
at com.megliosolutions.stormy.MainActivity.run(MainActivity.java:77)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
以上是我得到的错误。不知道从哪里开始。
有帮助吗？？
错误在这个函数中
public String getTimeZone() {
return mTimeZone;
}
返回null中的mTimeZone变量，所以，下面的代码引发异常：
TimeZone.getTimeZone(getTimeZone())
此外，在这个函数中：
private CurrentWeather getCurrentDetails(String jsonData) throws JSONException {
JSONObject forecast = new JSONObject(jsonData);
String timezone = forecast.getString("timezone");
Log.i(TAG, "From JSON: " + timezone);
JSONObject currently = forecast.getJSONObject("currently");
CurrentWeather currentWeather = new CurrentWeather();
currentWeather.setHumidity(currently.getDouble("humidity"));
currentWeather.setTime(currently.getLong("time"));
currentWeather.setIcon(currently.getString("icon"));
currentWeather.setPrecipChance(currently.getDouble("precipProbability"));
currentWeather.setSummary(currently.getString("summary"));
currentWeather.setTemperature(currently.getDouble("temperature"));
currentWeather.setTimeZone(timezone);
Log.d(TAG, currentWeather.getFormattedTime());
return new CurrentWeather();
}
您正在返回一个 new CurrentWeather() 对象。将其更改为：
return currentWeather;