android startActivityForResult

减少样板代码,解耦,灵活,易测试的目的

步骤

1.在app下的build.gradle中加入依赖:

implementation 'androidx.activity:activity:1.2.0-beta01'
implementation 'androidx.fragment:fragment:1.3.0-beta01'

2. 定义协议

新建一个Contract类，继承自ActivityResultContract<I,O>，其中，I是输入的类型，O是输出的类型。需要实现2个方法，createIntent和parseResult,输入类型I作为createIntent的参数，输出类型O作为parseResult方法的返回值

    static class ResultContract extends ActivityResultContract<Boolean, RecordGasGroupRequest.GasItemBean> {
        @NonNull
        @Override
        public Intent createIntent(@NonNull Context context, Boolean input) {
            Intent intent = new Intent(context, GroupAddGasActivity.class);
            intent.putExtra("b", input);
            return intent;
        }

        @Override
        public RecordGasGroupRequest.GasItemBean parseResult(int resultCode, @Nullable Intent intent) {
            if (resultCode == RESULT_OK) {
                return (RecordGasGroupRequest.GasItemBean) intent.getSerializableExtra("GasItemBean");
            }
            return null;
        }
    }

3. 注册协议，获取启动器-ActivityResultLauncher

注册协议，使用registerForActivityResult方法，该方法由ComponentActivity或者Fragment提供,接受2个参数，第一个参数就是我们定义的Contract协议，第二个参数是一个回调ActivityResultCallback<O>,其中O就是前面Contract的输出类型

    ActivityResultLauncher<Boolean> launcher = registerForActivityResult(new ResultContract(), new ActivityResultCallback<RecordGasGroupRequest.GasItemBean>() {
        @Override
        public void onActivityResult(RecordGasGroupRequest.GasItemBean gasItemBean) {
            LogUtils.log("返回 result:" + gasItemBean);
            if (gasItemBean != null) {
                mScanList.add(gasItemBean);
                mScanDataAdapter.notifyDataSetChanged();
            }
        }
    });

4. 最后，调用启动器的launch方法开启界面跳转

启动方法

   launcher.launch(true);

第二个界面与原来的写法一样

      setResult(RESULT_OK, new Intent().putExtra("GasItemBean", gasItemBean));
        finish();

用google 预定义的Contract

主要是减少了定义Contract类的书写，其他步骤一样，主要代码

    //注册协议
   ActivityResultLauncher<Intent> activityResultLauncher = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), new ActivityResultCallback<ActivityResult>() {
                @Override
                public void onActivityResult(ActivityResult result) {
                    LogUtils.log("activityResultLauncher:" +result.toString() );
                    if (result.getResultCode()== RESULT_OK) {
                        List<CheckContentBean> dataList = (List<CheckContentBean>) result.getData().getSerializableExtra("data");
                        mCheckContentList.clear();
                        mCheckContentList.addAll(dataList);
                        StringBuilder sb = new StringBuilder();
                        for (CheckContentBean bean : mCheckContentList) {
                            sb.append(bean.getContent()).append("\n");
                        }
                        if (sb.length() > 0) {
                            sb.deleteCharAt(sb.length() - 1);
                        }
                        mGasErrorView.setText(sb);
                        return;
                    }
                }
            }
                //启动方法
              activityResultLauncher.launch(intent);