第一行代码 14.5显示天气信息
在最后一部分的代码中，直接运行始终是不成功的。
报错信息是：出现了空指针异常的现象，其原因是findViewById这个方法返回的是null
这是我通过调试知道的。
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.coolweather.android/com.coolweather.android.WeatherActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3121)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3257)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:81)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1935)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7116)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:925)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at com.coolweather.android.WeatherActivity.showWeatherInfo(WeatherActivity.java:155)
at com.coolweather.android.WeatherActivity.onCreate(WeatherActivity.java:75)
at android.app.Activity.performCreate(Activity.java:7698)
at android.app.Activity.performCreate(Activity.java:7687)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3096)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3257)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:81)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1935)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7116)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:925)
原书上的代码是:
private void showWeatherInfo(Weather weather) {
String cityName = weather.basic.cityName;
String updateTime = weather.basic.update.updateTime.split(" ")[1];
String degree = weather.now.temperature + "℃";
String weatherInfo = weather.now.more.info;
titleCity.setText(cityName);
titleUpdateTime.setText(updateTime);
degreeText.setText(degree);
weatherInfoText.setText(weatherInfo);
forecastLayout.removeAllViews();
for (Forecast forecast : weather.forecastList) {
View view = LayoutInflater.from(this).inflate(R.layout.forecast_item,forecastLayout,false);
TextView dateText = (TextView)findViewById(R.id.date_text);
TextView infoText = (TextView)findViewById(R.id.info_text);
TextView maxText = (TextView)findViewById(R.id.max_text);
TextView minText = (TextView)findViewById(R.id.min_text);
dateText.setText(forecast.date);
infoText.setText(forecast.more.info);
maxText.setText(forecast.temperature.max);
minText.setText(forecast.temperature.min);
forecastLayout.addView(view);
}
if(weather.aqi!=null){
aqiText.setText(weather.aqi.city.aqi);
pm25Text.setText(weather.aqi.city.pm25);
}
String comfort = "舒适度："+weather.suggestion.comfort.info;
String carWash = "洗车指数： "+ weather.suggestion.carWash.info;
String sport = "运动建议： "+ weather.suggestion.sport.info;
comfortText.setText(comfort);
carWashText.setText(carWash);
sportText.setText(sport);
weatherLayout.setVisibility(View.VISIBLE);
}
解决方案：就中间部分的.findViewById（）方法前面加点东西。
至于为什么这样我也不是很清楚，大家想知道为什么可以去找一下资料。我参照的博客的链接:https://blog.csdn.net/yuxiaohui78/article/details/8195983?depth_1-utm_source=distribute.pc_relevant.none-task&utm_source=distribute.pc_relevant.none-task
private void showWeatherInfo(Weather weather) {
String cityName = weather.basic.cityName;
String updateTime = weather.basic.update.updateTime.split(" ")[1];
String degree = weather.now.temperature + "℃";
String weatherInfo = weather.now.more.info;
titleCity.setText(cityName);
titleUpdateTime.setText(updateTime);
degreeText.setText(degree);
weatherInfoText.setText(weatherInfo);
forecastLayout.removeAllViews();
for (Forecast forecast : weather.forecastList) {
View view = LayoutInflater.from(this).inflate(R.layout.forecast_item,forecastLayout,false);
TextView dateText = view.findViewById(R.id.date_text);
TextView infoText = view.findViewById(R.id.info_text);
TextView maxText = view.findViewById(R.id.max_text);
TextView minText = view.findViewById(R.id.min_text);
dateText.setText(forecast.date);
infoText.setText(forecast.more.info);
maxText.setText(forecast.temperature.max);
minText.setText(forecast.temperature.min);
forecastLayout.addView(view);
}
if(weather.aqi!=null){
aqiText.setText(weather.aqi.city.aqi);
pm25Text.setText(weather.aqi.city.pm25);
}
String comfort = "舒适度："+weather.suggestion.comfort.info;
String carWash = "洗车指数： "+ weather.suggestion.carWash.info;
String sport = "运动建议： "+ weather.suggestion.sport.info;
comfortText.setText(comfort);
carWashText.setText(carWash);
sportText.setText(sport);
weatherLayout.setVisibility(View.VISIBLE);
}
如果有用，可以点一下赞哟 ，嘿嘿
