Android:Intent

Intent intent = getIntent();

Intent intent2 = new Intent();

通常通过getIntent()方法获取到是非空的，即类似于：

intent：Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.example.menutest/.MainActivity }

intent2 是通过new 方式实例化的，肯定为null。

一般情况下我们需要用getIntent()方式来获取到本Activity的intent。

intent通常用于跳转,inent有个setAction()方法，官方文档的解释如下：

...setAction( action)

Set the general action to be performed.

Parameters:

action An action name, such as ACTION_VIEW. Application-specific actions should be prefixed with the vendor's package name.

Returns:

Returns the same Intent object, for chaining multiple calls into a single statement.

See Also:

getAction

实际上，设置action即，setAction(String action)这个方法通常是用来判断是点击了哪个按钮，然后来做相应的判断以及数据处理。

有如下场景，比如之前的那个记事本的应用实例里，

，

如何判断是点了添加新日记还是检测呢，那么就可以在public boolean onOptionsItemSelected(MenuItem item) {}这个方法里进行判断，如果点了添加新日记，那么我们就给新建一个intent0,给这个intent0绑定一个action即绑定一个字符串，这个所谓的action实际上就是一个字符串。具体代码如下：

 1 public boolean onOptionsItemSelected(MenuItem item) {
 2 
 3         switch (item.getItemId()) {
 4         case MENU_ITEM_INSERT:
 5 
 6             Intent intent0 = new Intent(this, MyDiaryEdit.class);
 7             //设置action，跳到第二个页面的时候就通过这个action来判断点了哪个按钮
 8             intent0.setAction(MyDiaryEdit.INSERT_TEXT_ACTION);
 9             System.out.println("intent0已经设置了Action，");
10             /*
11              * getIntent():Return the intent that started this activity 
12              * getIntent().getData(): Retrieve data this intent is operating on.
13              * Returns,The URI of the data this intent is targeting or null.
14              */
15             intent0.setData(getIntent().getData());//intent设置URI
16             System.out.println("Return the intent that started this activity,the intent:"+getIntent());
17             startActivity(intent0);
18             return true;
19 
20         case MENU_ITEM_EDIT:
21 
22             Intent intent1 = new Intent(this, MyDiaryEdit.class);
23             intent1.setAction(MyDiaryEdit.EDIT_TEXT_ACTION);
24             intent1.setData(item.getIntent().getData());
25             startActivity(intent1);
26             return true;
27 
28         case MENU_ITEM_DELETE:
29             Uri uri = ContentUris.withAppendedId(getIntent().getData(),
30                     getListView().getSelectedItemId());
31             getContentResolver().delete(uri, null, null);
32             rewindView();
33         }
34 
35         return super.onOptionsItemSelected(item);
36     }

第二个页面判断是点了哪个按钮的代码：

 1 protected void onCreate(Bundle savedInstanceState) {
 2         super.onCreate(savedInstanceState);
 3         setTheme(android.R.style.Theme_Black);
 4         //Return the intent that started this activity. 
 5         final Intent intent = getIntent();
 6         //获取intent里到底是绑定action字符串，下面用来判断是点了哪个按钮
 7         final String action = intent.getAction();
 8         setContentView(R.layout.mydiaryedit);//添加对应的layout
 9         System.out.println("intent.getAction():"+intent.getAction());
10         myToast("intent.getAction():"+intent.getAction());
11         TextView wyl_tv = (TextView) findViewById(R.id.wyl_txt);
12         wyl_tv.setText("intent.getAction():"+intent.getAction()+";

"
13                 + " URI uri = intent.getData(): "+intent.getData()+";

 MyDiaryEdit.java的intent："+getIntent());
14         mTitleText = (EditText) findViewById(R.id.title);
15         mBodyText = (EditText) findViewById(R.id.body);
16 
17         confirmButton = (Button) findViewById(R.id.confirm);
18         modifyButton = (Button) findViewById(R.id.modified);
19 
20         if (EDIT_TEXT_ACTION.equals(action)) {
21             /*
22              * EDIT_TEXT_ACTION.equals(action),EDIT_TEXT_ACTION就是前一个
23              * 页面中intent.setAction的时候设置的哪个字符串，这样就能够判断是不是点了新增日记的按钮了
24              */
25             mState = STATE_EDIT;
26             mTitleText.setEnabled(false);//设置为不可编辑
27             mBodyText.setEnabled(false);//设置不可编辑
28             modifyButton.setVisibility(View.VISIBLE);
29             mUri = intent.getData();
30             mCursor = managedQuery(mUri, projection, null, null, null);
31             mCursor.moveToFirst();
32             String title = mCursor.getString(1);
33             mTitleText.setTextKeepState(title);
34             String body = mCursor.getString(2);
35             mBodyText.setTextKeepState(body);
36 
37             setResult(RESULT_OK, new Intent(MyDiaryEdit.EDIT_TEXT_ACTION, mUri));
38             setTitle("编辑日记");
39         } else if (INSERT_TEXT_ACTION.equals(action)) {
40             mState = STATE_INSERT;
41             setTitle("新建日记");
42         } else {
43 
44             Log.e(TAG, "no such action error");
45             MyDiaryEdit.this.finish();
46 
47             return;
48         }
49 
50         confirmButton.setOnClickListener(new MyBtnOnClickListen());
51         modifyButton.setOnClickListener(new MyBtnOnClickListen());
52 
53     }