How to fix 'cannot be resolved or is not a type' error using Android Tutorial code?

Question

As suggested in other threads, I am following a tutorial in order to learn the basics of android application development. However, the code for the DisplayMessageActivity class as given here contains several errors:

• container can not be resolved or is not a field (line 16)
• Fragment cannot be resolved into a type (line 37)
• View cannot be resolved into a type (line 62)
• fragment_display_message cannot be resolved or is not a type (line 62).
• Wile trying to fix this error by my own a new error popped up out of nowhere at line 55: Class requires API level 11 (current min is 8);android.app.Fragment

According to another SO entry this is due to an ADT version mismatch. But this entry does not explain how to fix it.

How can this tutorial code be fixed so it compiles - or is there a 'working' tutorial available somewhere with actual working examples?

Here is the code so far:

package com.example.testapp;

import android.app.Fragment;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class DisplayMessageActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
//        setContentView(R.layout.activity_display_message);
//
//        if (savedInstanceState == null) {
//            getSupportFragmentManager().beginTransaction()
//                .add(R.id.container, new PlaceholderFragment())
//                .commit();
//        }

        // Get the message from the intent
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

        // Create the text view
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

        // Set the text view as the activity layout
        setContentView(textView);

    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() { }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                  Bundle savedInstanceState) {
              View rootView = inflater.inflate(R.layout.fragment_display_message,
                      container, false);
              return rootView;
        }
    }
}

Here is the content of the file res/layout/activity_main.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="horizontal" >

     <EditText android:id="@+id/edit_message"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:hint="@string/edit_message" />
     <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send"
        android:onClick="sendMessage" />
</LinearLayout>

and here the content of the file res/layout/activity_display_message.xml:

<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.testapp.DisplayMessageActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

Addendum:

• I tried to include missing libraries, and now most of the errors turned into a grey 'X' (which, I guess, is now a mere warning and can be ignored? Should it be fixed? If so, how?)
• The error regarding fragment_display_message stays as error, probably it is not defined (contrary to the example given.)

Answer 1

I was working my way through the same tutorial and I ran in to many of the same issues as you. One in particular had me stumped for an hour. I finally figured it out and here you go.

The error that the both of us got was the following:

fragment_display_message cannot be resolved or is not a type (line 62).

The fix is relatively simple, the reference to fragment_display_message should get changed to activity_display_message. Your new line in DisplayMessageActivity should now look like this:

View rootView = inflater.inflate(R.layout.activity_display_message, container, false);