我的findViewByid在擴展片段上變成紅色，即時通訊在onCreate方法上執行，不在onCreateView方法中

Question

通過標識為紅色的id查找視圖，我不是要對onCreateView執行此操作，請幫助我解決此類錯誤，我真的是android編程的新手

package com.example.mymonitoring;

public class MonitoringFragment extends Fragment {


private static final String TAG = "STATISTICACTIVITY";
private Button Temperature;
private Button Humidity;
private TextView t1;
private TextView t2;
private static TextView t3;
private static final String THINGSPEAK_CHANNEL_ID = "572138";
private static final String THINGSPEAK_API_KEY = "ND76MAN2CWQJG25G"; //GARBAGE KEY
private static final String THINGSPEAK_API_KEY_STRING = "ND76MAN2CWQJG25G";
/* Be sure to use the correct fields for your own app*/
private static final String THINGSPEAK_FIELD1 = "field1";
private static final String THINGSPEAK_FIELD2 = "field2";
private static final String THINGSPEAK_FIELD3 = "field3";
private static final String THINGSPEAK_UPDATE_URL = "https://api.thingspeak.com/update?";
private static final String THINGSPEAK_CHANNEL_URL = "https://api.thingspeak.com/channels/";
private static final String THINGSPEAK_FEEDS_LAST = "/feeds/last?";

private ThingSpeakChannel tsChannel;
private ThingSpeakLineChart tsChart;
private LineChartView chartView;

public MonitoringFragment() {
    // Required empty public constructor
}

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
return v;
}



@Override
public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);

        t1 = (TextView) findViewById(R.id.tempNumber);
        t2 = (TextView) findViewById(R.id.humidNumber);


        ThingSpeakChannel tsChannel = new ThingSpeakChannel(572138);
        tsChannel.setChannelFeedUpdateListener(new ThingSpeakChannel.ChannelFeedUpdateListener() {
            @Override
            public void onChannelFeedUpdated(long channelId, String channelName, ChannelFeed channelFeed) {
                // Make use of your Channel feed here!
                // Show Channel ID and name on the Action Bar
                //getSupportActionBar().setTitle(channelName);
                // Notify last update time of the Channel feed through a Toast message
                Date lastUpdate = channelFeed.getChannel().getUpdatedAt();
                //Toast.makeText(MonitoringFragment.this, lastUpdate.toString(), Toast.LENGTH_SHORT).show();
            }
        });
        tsChannel.loadChannelFeed();


        Temperature = (Button) findViewById(R.id.btnTemperature);
        Humidity = (Button) findViewById(R.id.btnHumidity);


        Temperature.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                findViewById(R.id.TemperatureLayout).setVisibility(View.VISIBLE);
                findViewById(R.id.HumidityLayout).setVisibility(View.GONE);


                final LineChartView chartView = (LineChartView) findViewById(R.id.TempChart);
                tsChart = new ThingSpeakLineChart(572138, 1);
                tsChart.setListener(new ThingSpeakLineChart.ChartDataUpdateListener() {
                    @Override
                    public void onChartDataUpdated(long channelId, int fieldId, String title, LineChartData lineChartData, Viewport maxViewport, Viewport initialViewport) {

                        Calendar calendar = Calendar.getInstance();
                        calendar.add(Calendar.MINUTE, -5);

                        tsChart.setNumberOfEntries(200);
                        // Set value axis labels on 10-unit interval
                        tsChart.setValueAxisLabelInterval(10);
                        // Set date axis labels on 5-minute interval
                        tsChart.setDateAxisLabelInterval(1);
                        // Show the line as a cubic spline
                        tsChart.useSpline(true);
                        // Set the line color
                        tsChart.setLineColor(Color.parseColor("#D32F2F"));
                        // Set the axis color
                        tsChart.setAxisColor(Color.parseColor("#455a64"));
                        // Set the starting date (5 minutes ago) for the default viewport of the chart
                        tsChart.setChartStartDate(calendar.getTime());

                        chartView.setLineChartData(lineChartData);
                        chartView.setMaximumViewport(maxViewport);
                        chartView.setCurrentViewport(initialViewport);
                    }
                });
                tsChart.loadChartData();

                try {
                    new FetchThingspeakTempTask().execute();
                } catch (Exception e) {
                    Log.e("ERROR", e.getMessage(), e);
                }
            }

        });



    Humidity.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            findViewById(R.id.HumidityLayout).setVisibility(View.VISIBLE);
            findViewById(R.id.TemperatureLayout).setVisibility(View.GONE);


            final LineChartView chartView = (LineChartView) findViewById(R.id.HumidChart);
            tsChart = new ThingSpeakLineChart(572138, 2);
            tsChart.setListener(new ThingSpeakLineChart.ChartDataUpdateListener() {
                @Override
                public void onChartDataUpdated(long channelId, int fieldId, String title, LineChartData lineChartData, Viewport maxViewport, Viewport initialViewport) {

                    Calendar calendar = Calendar.getInstance();
                    calendar.add(Calendar.MINUTE, -5);

                    tsChart.setNumberOfEntries(200);
                    // Set value axis labels on 10-unit interval
                    tsChart.setValueAxisLabelInterval(10);
                    // Set date axis labels on 5-minute interval
                    tsChart.setDateAxisLabelInterval(1);
                    // Show the line as a cubic spline
                    tsChart.useSpline(true);
                    // Set the line color
                    tsChart.setLineColor(Color.parseColor("#056604"));
                    // Set the axis color
                    tsChart.setAxisColor(Color.parseColor("#455a64"));
                    // Set the starting date (5 minutes ago) for the default viewport of the chart
                    tsChart.setChartStartDate(calendar.getTime());

                    chartView.setLineChartData(lineChartData);
                    chartView.setMaximumViewport(maxViewport);
                    chartView.setCurrentViewport(initialViewport);
                }
            });
            tsChart.loadChartData();
            try {
                new FetchThingspeakHumidTask().execute();
            }
            catch(Exception e){
                Log.e("ERROR", e.getMessage(), e);
            }


        }

    });
}

public class FetchThingspeakTempTask extends AsyncTask<Void, Void, String> {
    protected void onPreExecute() {
        t1.setText("Fetching Data from Server.Please Wait...");
    }
    protected String doInBackground(Void... urls) {
        try {
            URL url = new URL(THINGSPEAK_CHANNEL_URL + THINGSPEAK_CHANNEL_ID +
                    THINGSPEAK_FEEDS_LAST + THINGSPEAK_API_KEY_STRING + "=" +
                    THINGSPEAK_API_KEY + "");
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            try {
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
                StringBuilder stringBuilder = new StringBuilder();
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    stringBuilder.append(line).append("\n");
                }
                bufferedReader.close();
                return stringBuilder.toString();
            }
            finally{
                urlConnection.disconnect();
            }
        }
        catch(Exception e) {
            Log.e("ERROR", e.getMessage(), e);
            return null;
        }
    }
    protected void onPostExecute(String response) {
        if(response == null) {
            //Toast.makeText(MonitoringFragment.this, "There was an error", Toast.LENGTH_SHORT).show();
            return;
        }
        try {
            JSONObject channel = (JSONObject) new JSONTokener(response).nextValue();
            double v1 = channel.getDouble(THINGSPEAK_FIELD1);
            String field1 = Double.toString(v1);
            t1.setText(field1);


        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

public class FetchThingspeakHumidTask extends AsyncTask<Void, Void, String> {
    protected void onPreExecute() {
        t2.setText("Fetching Data from Server.Please Wait...");
    }
    protected String doInBackground(Void... urls) {
        try {
            URL url = new URL(THINGSPEAK_CHANNEL_URL + THINGSPEAK_CHANNEL_ID +
                    THINGSPEAK_FEEDS_LAST + THINGSPEAK_API_KEY_STRING + "=" +
                    THINGSPEAK_API_KEY + "");
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            try {
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
                StringBuilder stringBuilder = new StringBuilder();
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    stringBuilder.append(line).append("\n");
                }
                bufferedReader.close();
                return stringBuilder.toString();
            }
            finally{
                urlConnection.disconnect();
            }
        }
        catch(Exception e) {
            Log.e("ERROR", e.getMessage(), e);
            return null;
        }
    }
    protected void onPostExecute(String response) {
        if(response == null) {
           // Toast.makeText(MonitoringFragment.this, "There was an error", Toast.LENGTH_SHORT).show();
            return;
        }
        try {
            JSONObject channel = (JSONObject) new JSONTokener(response).nextValue();
            double v2 = channel.getDouble(THINGSPEAK_FIELD2);
            String field2 = new Double(v2).toString();
            t2.setText(field2);

        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

}

}

這是我的xml代碼fragment_monitoring.xml，findviewById標記為紅色，在擴展片段中的onCreate方法上執行

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context="com.example.mymonitoring.MonitoringFragment">

<!-- TODO: Update blank fragment layout -->
<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorGreyTransparent">

    <RelativeLayout
        android:id="@+id/statsLayoutToolbar"
        android:layout_width="match_parent"
        android:layout_height="50dp">

    </RelativeLayout>


        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar_stats"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:titleTextColor="@color/colorWhite">


        </android.support.v7.widget.Toolbar>


    </RelativeLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"

        android:orientation="horizontal"
        android:weightSum="100">


        <Button
            android:id="@+id/btnTemperature"
            android:layout_width="130dp"
            android:layout_height="60dp"
            android:layout_gravity="center"
            android:layout_weight="0"
            android:gravity="center"
            android:text="Temperature" />


        <Button
            android:id="@+id/btnHumidity"
            android:layout_width="130dp"
            android:layout_height="60dp"
            android:layout_gravity="center"
            android:layout_weight="0"
            android:gravity="center"
            android:text="Humidity" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="449dp"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="118dp"
        android:orientation="vertical"
        android:layout_alignParentLeft="true">

        <RelativeLayout
            android:id="@+id/TemperatureLayout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <include layout="@layout/tempdisplay" />

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:gravity="center"
                android:orientation="vertical">

                <TextView
                    android:layout_marginTop="300dp"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="Current Temperature :"
                    android:textColor="@color/colorBlack" />

                <TextView
                    android:id="@+id/tempNumber"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="........"
                    android:textColor="@color/colorBlack" />
                <TextView
                    android:layout_marginTop="10dp"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="Suggestion:"
                    android:textColor="@color/colorBlack" />

                <TextView
                    android:id="@+id/suggestionTemp"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="........"
                    android:textColor="@color/colorBlack" />


            </LinearLayout>
        </RelativeLayout>

        <RelativeLayout
            android:id="@+id/HumidityLayout"
            android:layout_width="match_parent"
            android:layout_height="match_parent">


            <include layout="@layout/humiddisplay" />
            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:gravity="center"
                android:orientation="vertical">

                <TextView
                    android:layout_marginTop="300dp"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="Current Humidity :"
                    android:textColor="@color/colorBlack" />

                <TextView
                    android:id="@+id/humidNumber"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="........"
                    android:textColor="@color/colorBlack" />
                <TextView
                    android:layout_marginTop="10dp"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="Suggestion:"
                    android:textColor="@color/colorBlack" />

                <TextView
                    android:id="@+id/suggestionHumid"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="........"
                    android:textColor="@color/colorBlack" />


            </LinearLayout>


        </RelativeLayout>

    </LinearLayout>
</RelativeLayout>

Answer 1

您正在Fragment（而不是活動findViewById()中調用findViewById() 。 Fragment沒有可調用的findViewById()方法。 您將必須在視圖上調用它，如下所示：

view.findViewById(R.id.testId)

如果您沒有片段視圖，則必須在onCreateView()中將其充氣。 請記住， onCreate()將在onCreateView()之前調用。

Answer 2

片段沒有findViewById()方法，所以它是紅色的，因為它不存在。

必須在View對象上或從Activity（這只是該Activity的根View的代理findViewById()上調用findViewById() ）。

無論如何，您也無法在Fragment的onCreate()方法中調用findViewById() ，因為onCreate()在onCreateView()之前執行，這意味着Fragment的View在那時為null。

v在您的Fragment中似乎也不是變量。

將您的代碼移動到onCreateView()或onViewCreated()並在View上進行findViewById()調用。

Answer 3

在片段上，要使用該方法，必須從父視圖中找到ID的地方調用它。

另外，您還必須考慮到視圖是在onCreateView之后創建的，因此您不會在onCreate上找到任何內容，因為該方法是在onCreateView之前調用的。

所以你應該在onCreateView上搜索這樣的視圖

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup 
    container, @Nullable Bundle savedInstanceState) {
    View root = inflater.inflate(R.layout.fragment_monitoring, container, false);
    TextView tempNumberTextView = root.findViewById(R.id.tempNumber)
    return root;
}