问声明textView在textView上给出了NullPointerException
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Stack Overflow用户

提问于 2015-11-29 11:03:17

回答 1查看 49关注 0票数 0

当来自“附近地点api”的评级小于或等于3为红色，大于3为绿色时，我尝试更改textView颜色，但我得到的NullPointerException如下所示：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setTextColor(int)' on a null object reference

下面是我的代码的一部分，我知道声明textView不在正确的位置。但是，我试图在onCreate中声明它，但是我得到了相同的错误。

活动的一部分：

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

    setContentView(R.layout.list_view_activity);
    myList = (ListView) findViewById(R.id.placesList);
}

public class readFromGooglePlaceAPI extends AsyncTask<String, Void, String> {

  @Override protected String doInBackground(String... param) {
    return readJSON(param[0]);
}

protected void onPostExecute(String str) {
    myArrayList = new ArrayList<GetterSetter>();

    String rating=" -NA-";
    try {

        JSONObject root = new JSONObject(str);
        JSONArray results = root.getJSONArray("results");

        for (int i = 0; i < results.length(); i++) {

            addValues = new GetterSetter();
            TextView rate = (TextView) findViewById(R.id.rating);

            JSONObject arrayItems = results.getJSONObject(i);
            if(!arrayItems.isNull("rating")){
                rating = arrayItems.getString("rating");

                if(Float.parseFloat(rating) <= 3){
                    rate.setTextColor(Color.RED);
                }
                else if(Float.parseFloat(rating) > 3){
                    rate.setTextColor(Color.GREEN);
                }
            }

            addValues.setRating(rating);
            myArrayList.add(addValues);
        }
    } catch (Exception e) {
        Log.e("Error", "Exception ..." , e);
    }
    adapter = new CustomAdapter(ListActivity.this, R.layout.list_row, myArrayList);
    myList.setAdapter(adapter);

}

}

list_view_activity.xml

<LinearLayout 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"
android:orientation="vertical"
tools:context=".MainActivity" >
<ListView
    android:id="@+id/placesList"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="1.0"
    android:paddingTop="70dp"
    android:divider="@drawable/divider"
    android:dividerHeight="1px"
    android:cacheColorHint="#00000000"
    android:listSelector="@drawable/listview_selector">
</ListView>
</LinearLayout>

list_row.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="20dp"
android:paddingRight="20dp" >
<TextView
    android:id="@+id/ratingRext"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_alignParentRight="true"
    android:layout_alignRight="@id/name"
    android:gravity="center_vertical"
    android:minHeight="?android:attr/listPreferredItemHeight"
    android:paddingRight="20dp"
    android:text="Rating :"
    android:textSize="14sp"
    android:textColor="#282f8d" />

<TextView
    android:id="@+id/rating"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_alignParentRight="true"
    android:layout_alignRight="@id/ratingRext"
    android:gravity="center_vertical"
    android:minHeight="?android:attr/listPreferredItemHeight"
    android:textSize="12sp" />
 </RelativeLayout>