[英]RecyclerView Null Pointer Exception
我是Android Studio的新用戶,並且發現了類似的問題但沒有回復適用於我當前的實例。 我一直在嘗試使用RecyclerViews,並且每當我用它打開一個活動時都會收到以下錯誤消息。 代碼不顯示任何錯誤。
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.lucasrizzotto.edgeweather/com.lucasrizzotto.edgeweather.ui.HourlyForecastActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
這是我的適配器:
public class HourAdapter extends RecyclerView.Adapter<HourAdapter.HourViewHolder> {
private Hour[] mHours;
public HourAdapter(Hour[] hours) {
mHours = hours;
}
@Override
public HourViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).
inflate(R.layout.hourly_list_item, parent, false);
HourViewHolder viewHolder = new HourViewHolder(view);
return viewHolder;
}
@Override
public void onBindViewHolder(HourViewHolder holder, int position) {
holder.bindHour(mHours[position]);
}
@Override
public int getItemCount() {
return mHours.length;
}
public class HourViewHolder extends RecyclerView.ViewHolder {
public TextView mTimeLabel;
public TextView mTemperatureLabel;
public TextView mSummaryLabel;
public ImageView mIconImageView;
public HourViewHolder(View itemView) {
super(itemView);
mTimeLabel = (TextView) itemView.findViewById(R.id.timeLabel);
mTemperatureLabel = (TextView) itemView.findViewById(R.id.temperatureLabel);
mSummaryLabel = (TextView) itemView.findViewById(R.id.summaryLabel);
mIconImageView = (ImageView) itemView.findViewById(R.id.iconImageView);
}
public void bindHour(Hour hour) {
mTimeLabel.setText(hour.getHour());
mSummaryLabel.setText(hour.getSummary());
mTemperatureLabel.setText((int)hour.getTemperature());
mIconImageView.setImageResource(hour.getIconId());
}
}
}
和我的Activity類(請記住我正在使用ButterKnife插件來避免樣板代碼)
public class HourlyForecastActivity extends AppCompatActivity {
private Hour[] mHours;
@BindView(R.id.recyclerView) RecyclerView mRecyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_hourly_forecast);
Intent intent = getIntent();
Parcelable[] parcelables = intent.getParcelableArrayExtra(MainActivity.HOURLY_FORECAST);
mHours = Arrays.copyOf(parcelables, parcelables.length, Hour[].class);
HourAdapter adapter = new HourAdapter(mHours);
mRecyclerView.setAdapter(adapter);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(layoutManager);
mRecyclerView.setHasFixedSize(true);
}
}
我在俯瞰什么?
提前感謝您的智慧!
試着打電話:
ButterKnife.bind(this);
設置內容視圖后
由於您沒有以傳統方式執行此操作,因此您需要實際調用bind()。
您正在使用ButterKnife綁定視圖,這是很好的。
但似乎你忘了為你當前的Activity 初始化ButterKnife 。
就這樣做,
ButterKnife.bind(this);
在這一行之后,
setContentView(R.layout.activity_hourly_forecast);
這將為您當前的Activity初始化ButterKnife,您將能夠正確引用您的布局中的RecyclerView。
希望能幫助到你。
基本上你需要初始化mRecyclerView
例如
mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
但在你的情況下,你使用ButterKnife庫。
所以你需要在setContentView(R.layout.activity_hourly_forecast)之后調用它的bind()方法;
setContentView(R.layout.activity_hourly_forecast);
ButterKnife.bind(this);
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