Question

我的自定义ArrayAdapter中存在错误。 Android Studio会一直显示View listItemView = convertView;，并显示unreachable statement。

package com.example.android.miwok;

import android.app.Activity;
import android.support.annotation.NonNull;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import java.util.ArrayList;

public class WordAdapter extends ArrayAdapter<Word> {

    public WordAdapter(Activity context, ArrayList<Word> words) {
        // Here, we initialize the ArrayAdapter's internal storage for the context and the list.
        // the second argument is used when the ArrayAdapter is populating a single TextView.
        // Because this is a custom adapter for two TextViews and an ImageView, the adapter is not
        // going to use this second argument, so it can be any value. Here, we used 0.
        super(context, 0, words);
    }

        @Override
        public View getView(int position, View convertView, ViewGroup parent){
            return super.getView(position, convertView, parent);

            // Check if the existing view is being reused, otherwise inflate the view
            View listItemView = convertView;

            if (listItemView == null) {
                listItemView = LayoutInflater.from(getContext()).inflate(
                        R.layout.list_item, parent, false);
            }

            // Get the {@link AndroidFlavor} object located at this position in the list
            Word currentWord = getItem(position);

            // Find the TextView in the list_item.xml layout with the ID version_name
            TextView defaultTextView = (TextView) listItemView.findViewById(R.id.default_text_view);
            // Get the version name from the current AndroidFlavor object and
            // set this text on the name TextView
            defaultTextView.setText(currentWord.getDefaultTranslation());

            // Find the TextView in the list_item.xml layout with the ID version_number
            TextView miwokTextView = (TextView) listItemView.findViewById(R.id.miwok_text_view);
            // Get the version number from the current AndroidFlavor object and
            // set this text on the number TextView
            miwokTextView.setText(currentWord.getMiwokTranslation());

            // Return the whole list item layout (containing 2 TextViews and an ImageView)
            // so that it can be shown in the ListView
            return listItemView;
        }

}

它使用我Word类的新创建的对象：

package com.example.android.miwok;

public class Word {

    /** Default translation for the word */
    private String mDefaultTranslation;

    /** Miwok translation for the word */
    private String mMiwokTranslation;

    /**
     * Create a new Word object.
     *
     * @param defaultTranslation is the word in a language that the user is already familiar with
     *                           (such as English)
     * @param miwokTranslation is the word in the Miwok language
     */
    public Word(String defaultTranslation, String miwokTranslation) {
        mDefaultTranslation = defaultTranslation;
        mMiwokTranslation = miwokTranslation;
    }

    /**
     * Get the default translation of the word.
     */
    public String getDefaultTranslation() {
        return mDefaultTranslation;
    }

    /**
     * Get the Miwok translation of the word.
     */
    public String getMiwokTranslation() {
        return mMiwokTranslation;
    }

}

从此Activity调用

package com.example.android.miwok;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ListView;

import java.util.ArrayList;

public class NumbersActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_numbers);

        // Create a list of words
        ArrayList<Word> words = new ArrayList<Word>();
        words.add(new Word("one", "lutti"));
        words.add(new Word("two", "otiiko"));
        words.add(new Word("three", "tolookosu"));
        words.add(new Word("four", "oyyisa"));
        words.add(new Word("five", "massokka"));
        words.add(new Word("six", "temmokka"));
        words.add(new Word("seven", "kenekaku"));
        words.add(new Word("eight", "kawinta"));
        words.add(new Word("nine", "wo’e"));
        words.add(new Word("ten", "na’aacha"));

        // Create an {@link WordAdapter}, whose data source is a list of {@link Word}s. The
        // adapter knows how to create list items for each item in the list.
        WordAdapter adapter = new WordAdapter(this, words);

        // Find the {@link ListView} object in the view hierarchy of the {@link Activity}.
        // There should be a {@link ListView} with the view ID called list, which is declared in the
        // activity_numbers.xml layout file.
        ListView listView = (ListView) findViewById(R.id.list);

        // Make the {@link ListView} use the {@link WordAdapter} we created above, so that the
        // {@link ListView} will display list items for each {@link Word} in the list.
        listView.setAdapter(adapter);
    }
}

Answer 1

在方法声明后直接有一个return语句，返回后不会发生任何事情。

@Override
public View getView(int position, View convertView, ViewGroup parent){
    //You might want to put your code here
    return super.getView(position, convertView, parent);
    // Nothing can happen beyond this point

    // Check if the existing view is being reused, otherwise inflate the view
    View listItemView = convertView;

该方法中没有任何内容被执行，你可能并不意味着要进行第一次回归。

Answer 2

这有效......

public class WordAdapter extends ArrayAdapter<Word>  {

    /**
     * Create a new {@link WordAdapter} object.
     *
     * @param context is the current context (i.e. Activity) that the adapter is being created in.
     * @param words is the list of {@link Word}s to be displayed.
     * @param //colorResourceId is the resource ID for the background color for this list of words
     */
    public WordAdapter(Activity context, ArrayList<Word> words) {
        super(context, 0, words);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // Check if an existing view is being reused, otherwise inflate the view
        View listItemView = convertView;
        if (listItemView == null) {
            listItemView = LayoutInflater.from(getContext()).inflate(
                    R.layout.list_item, parent, false);
        }

            // Get the {@link AndroidFlavor} object located at this position in the list
            Word currentWord = getItem(position);

            // Find the TextView in the list_item.xml layout with the ID version_name
            TextView defaultTextView = (TextView) listItemView.findViewById(R.id.default_text_view);
            // Get the version name from the current AndroidFlavor object and
            // set this text on the name TextView
            defaultTextView.setText(currentWord.getDefaultTranslation());

自定义ArrayAdapter中的无法访问的语句

2 个答案: