Why doesn't the code from the Android SDK tutorials work out of the box?

Am I missing something here?

I follow the instructions exactly on this page (and some of the other tutorials) but they always seem to be missing some key information as they don't work out of the box.

I added a bunch of packages that seemed like were 开发者_运维百科missing, but now I'm stuck.

http://developer.android.com/resources/tutorials/views/hello-gridview.html

Description Resource Path Location Type Conversion to Dalvik format failed with error 1 HelloGrid Unknown Android Packaging Problem

And a whole bunch of these for each of the drawable.sample_* references

Description Resource Path Location Type R.drawable.sample_0 cannot be resolved ImageAdapter.java /HelloGrid/src/com/example/ImageAdapter line 51 Java Problem

package com.example.HelloGrid;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.GridView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;

import com.example.ImageAdapter.ImageAdapter;

public class HelloGrid extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        GridView gridview = (GridView) findViewById(R.id.gridview);
        gridview.setAdapter(new ImageAdapter(this));

        gridview.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
                Toast.makeText(HelloGrid.this, "" + position, Toast.LENGTH_SHORT).show();
            }
        });
    }
}

package com.example.ImageAdapter;
import android.R;
import android.R.drawable;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class ImageAdapter extends BaseAdapter {
    private Context mContext;

    public ImageAdapter(Context c) {
        mContext = c;
    }

    public int getCount() {
        return mThumbIds.length;
    }

    public Object getItem(int position) {
        return null;
    }

    public long getItemId(int position) {
        return 0;
    }

    // create a new ImageView for each item referenced by the Adapter
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {  // if it's not recycled, initialize some attributes
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);
        } else {
            imageView = (ImageView) convertView;
        }

        imageView.setImageResource(mThumbIds[position]);
        return imageView;
    }

    // references to our images
    private Integer[] mThumbIds = {
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7
    };
}

As you can see I have all the images loaded in the /drawable directory

Description Resource Path Location Type R.drawable.sample_0 cannot be resolved ImageAdapter.java /HelloGrid/src/com/example/ImageAdapter line 51 Java Problem

You are missing your drawable resources. That was covered in step #2 in the instructions supplied in the tutorial.

Remove import android.R;

This confuses Eclipses' R;

That's why it cannot locate the images.

Also, you can simply place it inside the pre-created drawable directories in res.( e.g. drawable-hdpi, etc.)

I had this issue too, and resolved it by fixing this line:

Toast.makeText(HelloGridView.this, "" + position, Toast.LENGTH_SHORT).show();

to

Toast.makeText(HelloGridViewActivity.this, "" + position, Toast.LENGTH_SHORT).show();

I have the solution:

package com.gridview.test;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.GridView;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Toast;
import android.widget.BaseAdapter;
import android.content.Context;
import android.view.ViewGroup;
import android.widget.ImageView;


public class HelloGridView extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        GridView gridview = (GridView) findViewById(R.id.gridview);
        gridview.setAdapter(new ImageAdapter(this));

        gridview.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
                Toast.makeText(HelloGridView.this, "" + position, Toast.LENGTH_SHORT).show();
            }
        });
   }



    public class ImageAdapter extends BaseAdapter {
        private Context mContext;

        public ImageAdapter(Context c) {
            mContext = c;
        }

        public int getCount() {
            return mThumbIds.length;
        }

        public Object getItem(int position) {
            return null;
        }

        public long getItemId(int position) {
            return 0;
        }

        // create a new ImageView for each item referenced by the Adapter
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView imageView;
            if (convertView == null) {  // if it's not recycled, initialize some attributes
                imageView = new ImageView(mContext);
                imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                imageView.setPadding(8, 8, 8, 8);
            } else {
                imageView = (ImageView) convertView;
            }

            imageView.setImageResource(mThumbIds[position]);
            return imageView;
        }

        // references to our images
        private Integer[] mThumbIds = {
                R.drawable.sample_2, R.drawable.sample_3,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7,
                R.drawable.sample_0, R.drawable.sample_1,
                R.drawable.sample_2, R.drawable.sample_3,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7,
                R.drawable.sample_0, R.drawable.sample_1,
                R.drawable.sample_2, R.drawable.sample_3,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7
        };
    }
}

Adding imports solved the problem for me.
And I found out that actually in Eclipse they can be imported automatically:

"Tip: After you have pasted sample code into an Eclipse project, press Ctrl (or Cmd) + Shift + O to import the required packages"

Hope this refresh what have been missed.

It looks like the tutorials are missing some of the package information, but if you're using eclipse it should handle most of that for you.