Android百日程序：Intent传递数据

上一遍是回传数据，当热Activity之间是可以利用Intent很方便地传递很多数据的。

本章就两个Activity之间传递String和Int数据。

1 主要界面：

2 点击按钮之后，就进入第二个activity

这个时候会利用Toast机制显示第一个activity传递什么String和Int给第二个activity。

3 然后点击“return to main activity”，回到第一个activity

同样会显示回传的信息

这样可以在activity之间来回传递需要的信息。

新建项目；

1 首先设计主界面，代码：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.intenttest.MainActivity" >

    <Button
        android:id="@+id/seconde_activity_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/activate_secondary"
        android:onClick="onClick" />

</LinearLayout>

2 构建第二个activity的界面，代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/txt_username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="@string/secondary_activity" />

    <Button
        android:id="@+id/btn_OK"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="onClick"
        android:text="@string/return_to_main_activity" />

</LinearLayout>

3 第一个activity的代码:

package com.example.intenttest;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends Activity {
	/*
	 * An integer value that identifies an activity you are calling. When an
	 * Activity returns a value, you must have a way to identify it If the
	 * request code is set to -1, then calling it using the
	 * startActivityForResult() method is equivalent to calling it using the
	 * startActivity() method. That is, no result will be returned.
	 */
	int requestCode = 1;

	public static <T> boolean equ(T t1, T t2) {
		return t1 == t2;
	}

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
	}

	public void onClick(View view) {
		Intent i = new Intent("su.bill.intenttest.SecondaryActivity");
		i.putExtra(SecondaryActivity.extraStr, "Give you a string");
		i.putExtra(SecondaryActivity.extraInt, 15);

		Bundle extras = new Bundle();
		extras.putString(SecondaryActivity.extraStr2, "String in data");
		extras.putInt(SecondaryActivity.extraInt2, 22);

		i.putExtras(extras);

		startActivityForResult(i, requestCode);
	}

	@Override
	public void onActivityResult(int reqCode, int resCode, Intent data) {
		if (equ(reqCode, requestCode) && equ(resCode, RESULT_OK)) {
			Toast.makeText(this,
					Integer.toString(data.getIntExtra(SecondaryActivity.extraInt3, 0)),
					Toast.LENGTH_SHORT).show();
			
			Toast.makeText(this,
					data.getDataString(), 
					Toast.LENGTH_SHORT).show();
		}
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// Handle action bar item clicks here. The action bar will
		// automatically handle clicks on the Home/Up button, so long
		// as you specify a parent activity in AndroidManifest.xml.
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}
}

1） 让Intent带上String数据：

i.putExtra(SecondaryActivity.extraStr, "Give you a string");

2） 让Intent带上Int数据
i.putExtra(SecondaryActivity.extraInt, 15);

3）还可以使用Bundle数据结构，直接带上String和Int数据：
Bundle extras = new Bundle();
extras.putString(SecondaryActivity.extraStr2, "String in data");
extras.putInt(SecondaryActivity.extraInt2, 22);
i.putExtras(extras);

回传调用的函数onActivityResult还是和前一章一样。使用了Toast显示多个回传的数据。

4 然后是第二个activity的逻辑代码：

package com.example.intenttest;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class SecondaryActivity extends Activity {
	public static String extraStr = "extra_string";
	public static String extraInt = "extra_int";
	public static String extraStr2 = "extra_string_2";
	public static String extraInt2 = "extra_int_2";
	public static String extraInt3 = "extra_int_3";

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.secondary_activity);

		Toast.makeText(this, getIntent().getStringExtra(extraStr),
				Toast.LENGTH_SHORT).show();
		Toast.makeText(this, String.valueOf(getIntent().getIntExtra(extraInt, 0)),
				Toast.LENGTH_SHORT).show();

		Bundle bundle = getIntent().getExtras();
		Toast.makeText(this, bundle.getString(extraStr2), Toast.LENGTH_SHORT)
				.show();
		Toast.makeText(this, Integer.toString(bundle.getInt(extraInt2)),
				Toast.LENGTH_SHORT).show();
	}

	public void onClick(View v) {
		Intent i = new Intent();

		i.putExtra(extraInt3, 28);

		i.setData(Uri.parse("pass integer back to main activity"));

		setResult(RESULT_OK, i);

		finish();
	}

}

1）取得Intent中的String数据

getIntent().getStringExtra(extraStr)

2）取得Intent中的Int数据：

getIntent().getIntExtra(extraInt, 0)

3）回传String数据：

i.setData(Uri.parse("pass integer back to main activity"));

4）回传函数：

setResult(RESULT_OK, i);

也是利用Toast数据显示。