android 分享或者调用系统或者其他app时 应注意！ startActivityForResult() 使用

//判断是否有相应的Activity来接受intent
PackageManager packageManager = getPackageManager();
List<ResolveInfo> activities = packageManager.queryIntentActivities(intent, 0);
boolean isIntentSafe = activities.size() > 0;
如果 isIntentSafe 为true 则有相应的Activity来接受 反之则无。

//始终弹出dialog让用户选择
Intent chooser = Intent.createChooser(intent, "请选择");
始终让用户选择使用什么App打开

判断启动：

if (isIntentSafe){
    startActivity(chooser);
}

跳转很简单：
//跳转到通讯录

Intent pickContactIntent = new Intent(Intent.ACTION_PICK, Uri.parse("content://contacts"));
pickContactIntent.setType(ContactsContract.CommonDataKinds.Phone.CONTENT_TYPE);
然后启动：
startActivityForResult(pickContactIntent ,1); //传一个1过去，当在返回的时候看是否返回成功的关键


在Acitivity中实现：

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == 1){
        if (resultCode == -1){//返回结果的code是-1则成功，0则是空
            Uri uri = data.getData();
            String[] projection = {ContactsContract.CommonDataKinds.Phone.NUMBER, ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME};
            Cursor cursor = getContentResolver().query(uri, projection,null,null,null);
            cursor.moveToFirst();
            int column1 = cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER);
            int column2 = cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME);
            String number = cursor.getString(column1);
            String name = cursor.getString(column2);
            Log.i("CCCCCCCCCCCCCCC",number);
            Log.i("NNNNNNNNNNNNNNN",name);
        }
    }
}