android 日常（一）

• 给LinearLayout添加滚动条

<?xml version="1.0" encoding="utf-8"?> 
<ScrollView      
xmlns:android="[http://schemas.android.com/apk/res/android](http://schemas.android.com/apk/res/android)"  
android:layout_width="fill_parent" 
android:layout_height="fill_parent"
android:scrollbars="vertical"
android:fadingEdge="vertical"
>      
    <LinearLayout
        android:layout_width="fill_parent" 
        android:layout_height="fill_parent"
        android:orientation="vertical" >      
    </LinearLayout> 
</ScrollView> 

<scrollView>下只能有一个子控件

• Activity之间对象传递
  1.所传的对象 实现接口 Serializable:
  <pre>
  public class Person implements Serializable {
  </pre>
  2.传递对象的原始页面调用intent.putExtra()即可：
  <pre>
  Intent intent = new Intent();
  Person obj = new Person(wg_name.getText().toString(),wg_age.getText().toString());
  intent.putExtra("Person", obj);
  intent.setClass(Demo_trans_objectActivity.this, OtherActivity.class);
  startActivity(intent);
  </pre>
  3.接收对象的界面使用getIntent().getSerializableExtra()获取对象：
  <pre>
  Person p = (Person) getIntent().getSerializableExtra("Person");
  ((TextView)findViewById(R.id.name)).setText(p.name);
  ((TextView)findViewById(R.id.age)).setText(p.age);
  </pre>

---

• 给Layout设置边框
  <pre>
  <?xml version="1.0" encoding="utf-8"?>
  <shape xmlns:android="http://schemas.android.com/apk/res/android" >
  <solid android:color="#FFFFFF" />
  <stroke
  android:width="0.01dp"
  android:color="#FFFFFF" />
  <padding
  android:bottom="1dp"
  android:left="0.5dp"
  android:right="0.5dp"
  android:top="0dp" />
  </shape>
  </pre>
  然后给layout指定background属性就可以

• 通过控制台将sqlite数据库文件导出
  <pre>
  adb pull /data/data/com.yourproject/databases/testdatabase.db d:\shownearby.db
  </pre>

• EditText添加监听
  监听EditText的变化
  <pre>
  et.addTextChangedListener(new TextWatcher() {
  @Override
  public void beforeTextChanged(CharSequence s, int start, int count,int after) {
  tv.setText("还能输入"+Rest_Length+"个字");
  }
  @Override
  public void afterTextChanged(Editable s) {
  tv.setText("还能输入"+Rest_Length+"个字");
  }
  @Override
  public void onTextChanged(CharSequence s, int start, int before, int count) {
  if(Rest_Length>0){
  Rest_Length = MAX_LENGTH - et.getText().length();
  }
  }
  });
  </pre>

• java中判断字符串是否为数字的方法的几种方法

• 清空listview(添加了listAdapter)的方法

1. listView.setAdapter(null);
2. listAdapter.clear();
   listAdapter.notifyDataSetChanged() ;