Android Performance Optimization

The following will implement a performance optimized version of the adapter from the previous example.

Create the following MyPerformanceArrayAdapter class.

package de.vogella.android.listactivity;

import android.app.Activity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

public class MyPerformanceArrayAdapter extends ArrayAdapter<String> {
  private final Activity context;
  private final String[] names;

  static class ViewHolder {
    public TextView text;
    public ImageView image;
  }

  public MyPerformanceArrayAdapter(Activity context, String[] names) {
    super(context, R.layout.rowlayout, names);
    this.context = context;
    this.names = names;
  }

  @Override
  public View getView(int position, View convertView, ViewGroup parent) {
    View rowView = convertView;
    if (rowView == null) {
      LayoutInflater inflater = context.getLayoutInflater();
      rowView = inflater.inflate(R.layout.rowlayout, null);
      ViewHolder viewHolder = new ViewHolder();
      viewHolder.text = (TextView) rowView.findViewById(R.id.TextView01);
      viewHolder.image = (ImageView) rowView
          .findViewById(R.id.ImageView01);
      rowView.setTag(viewHolder);
    }

    ViewHolder holder = (ViewHolder) rowView.getTag();
    String s = names[position];
    holder.text.setText(s);
    if (s.startsWith("Windows7") || s.startsWith("iPhone")
        || s.startsWith("Solaris")) {
      holder.image.setImageResource(R.drawable.no);
    } else {
      holder.image.setImageResource(R.drawable.ok);
    }

    return rowView;
  }
} 

Use your new adapter in your activity. If you run the application it should look the same but it will be much faster, especially for large datasets.

package de.vogella.android.listactivity;

import android.app.ListActivity;
import android.os.Bundle;

public class MyListActivity extends ListActivity {
  public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    String[] values = new String[] { "Android", "iPhone", "WindowsMobile",
        "Blackberry", "WebOS", "Ubuntu", "Windows7", "Max OS X",
        "Linux", "OS/2" };
    setListAdapter(new MyPerformanceArrayAdapter(this, values));
  }

} 

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