HelloWorld for Android-优快云博客

本文介绍了一个简单的Android应用示例，该应用能在EditText输入内容，并实时显示在TextView中。通过这个例子，作者练习了View、Listener、findViewById等基本概念，并介绍了如何使用Android SDK帮助文档。

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练练手，熟悉一下Android的开发。Android SDK的帮助文档很有帮助，仔细读读，路径为：
android-sdk-windows\docs
第一个例子：
在EditText中输入，在TextView中及时显示。练习了View, Listener, findViewById, getString(resID), Log.

package ian.study.demos;

import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.widget.EditText;
import android.widget.TextView;

public class HelloWrold extends Activity {
    static final String STR_DEFAULT_SAY = "It's not my first Android App. LoL";
    private  TextView tvSay;
    private  EditText etSay;

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

        tvSay = (TextView)findViewById(R.id.tvSay);
        tvSay.setText(STR_DEFAULT_SAY);

        etSay = (EditText)findViewById(R.id.etSay);
        etSay.setText(R.string.saysomething);

        etSay.addTextChangedListener(new TextWatcher(){
        	  public void afterTextChanged(Editable s) {
        		  Log.d(getString(R.string.app_name), "after changed");
              }

              public void beforeTextChanged(CharSequence s, int start, int count, int after) {
              }

              public void onTextChanged(CharSequence s, int start, int before, int count) {
            	  tvSay.setText(etSay.getText());
            	  Log.d(getString(R.string.app_name), "on changed");
              }
        });

    }
}